SCHEDULE 13G

Amendment No. 6
Synaptics Incorporated
Common Stock
Cusip #87157D109


Cusip #87157D109
Item 1:	Reporting Person - FMR LLC
Item 4:	Delaware
Item 5:	550
Item 6:	0
Item 7:	2,210,725
Item 8:	0
Item 9:	2,210,725
Item 11:	6.514%
Item 12:	    HC


Cusip #87157D109
Item 1:	Reporting Person - Edward C. Johnson 3d
Item 4:	United States of America
Item 5:	0
Item 6:	0
Item 7:	2,210,725
Item 8:	0
Item 9:	2,210,725
Item 11:	6.514%
Item 12:	IN




	SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)



Item 1(a).	Name of Issuer:

		Synaptics Incorporated

Item 1(b).	Name of Issuer's Principal Executive Offices:

		3120 Scott Blvd
		Suite 130
		Santa Clara, CA  95054


Item 2(a).	Name of Person Filing:

		FMR LLC

Item 2(b).	Address or Principal Business Office or, if None,
Residence:

		82 Devonshire Street, Boston,
Massachusetts  02109

Item 2(c).	Citizenship:

		Not applicable

Item 2(d).	Title of Class of Securities:

		Common Stock

Item 2(e).	CUSIP Number:

		87157D109

Item 3.	This statement is filed pursuant to Rule 13d-1(b) or 13d-2(b)
and the person filing, FMR LLC, is a parent holding company
in accordance with Section 240.13d-1(b)(ii)(G).  (Note:  See
Item 7).

Item 4.	Ownership

	(a)	Amount Beneficially Owned:	2,210,725

	(b)	Percent of Class:	6.514%

	(c)	Number of shares as to which such
person has:

	(i)	sole power to vote or to direct
the vote:	550

	(ii)	shared power to vote or to
direct the vote:	0

	(iii)	sole power to dispose or to
direct the disposition of:	2,210,725

	(iv)	shared power to dispose or to
direct the disposition of:	0



Item 5.	Ownership of Five Percent or Less of a Class.

	Not applicable.

Item 6.	Ownership of More than Five Percent on Behalf of Another
Person.

	Various persons have the right to receive or the power to
direct the receipt of dividends from, or the proceeds from the
sale of, the Common Stock of Synaptics Incorporated.  No one
person's interest in the Common Stock of Synaptics
Incorporated is more than five percent of the total outstanding
Common Stock.

Item 7.	Identification and Classification of the Subsidiary Which
Acquired the Security Being Reported on By the Parent
Holding Company.

	See attached Exhibit A.

Item 8.	Identification and Classification of Members of
the Group.

	Not applicable.  See attached Exhibit A.

Item 9.	Notice of Dissolution of Group.

	Not applicable.

Item 10.	Certification.

	By signing below I certify that, to the best of my knowledge
and belief, the securities referred to above were acquired in the
ordinary course of business and were not acquired for the
purpose of and do not have the effect of changing or
influencing the control of the issuer of such securities and
were not acquired in connection with or as a participant in any
transaction having such purpose or effect.

Signature

	After reasonable inquiry and to the best of my knowledge and
belief, I certify that the information set forth in this statement
is true, complete and correct.

November 09, 2009
Date

 /s/ Scott C. Goebel
Signature

Scott C. Goebel
Duly authorized under Power of Attorney
effective as of June 1, 2008 by and on behalf of FMR LLC
and its direct and indirect  subsidiaries


	SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)



	Pursuant to the instructions in Item 7 of Schedule 13G,
Fidelity Management & Research Company ("Fidelity"), 82
Devonshire Street, Boston, Massachusetts 02109, a wholly-
owned subsidiary of FMR LLC and an investment adviser
registered under Section 203 of the Investment Advisers Act
of 1940, is the beneficial owner of 2,208,925 shares or 6.509%
of the Common Stock outstanding of Synaptics Incorporated
("the Company") as a result of acting as investment adviser to
various investment companies registered under Section 8 of
the Investment Company Act of 1940.

	Edward C. Johnson 3d and FMR LLC, through its
control of Fidelity, and the funds each has sole power to
dispose of the 2,208,925 shares owned by the Funds.

	Members of the family of Edward C. Johnson 3d,
Chairman of FMR LLC, are the predominant owners, directly
or through trusts, of Series B voting common shares of FMR
LLC, representing 49% of the voting power of FMR LLC.
The Johnson family group and all other Series B shareholders
have entered into a shareholders' voting agreement under
which all Series B voting common shares will be voted in
accordance with the majority vote of Series B voting common
shares.  Accordingly, through their ownership of voting
common shares and the execution of the shareholders' voting
agreement, members of the Johnson family may be deemed,
under the Investment Company Act of 1940, to form a
controlling group with respect to FMR LLC.

	Neither FMR LLC nor Edward C. Johnson 3d,
Chairman of FMR LLC, has the sole power to vote or direct
the voting of the shares owned directly by the Fidelity Funds,
which power resides with the Funds' Boards of Trustees.
Fidelity carries out the voting of the shares under written
guidelines established by the Funds' Boards of Trustees.

	Pyramis Global Advisors Trust Company ("PGATC"),
900 Salem Street, Smithfield, Rhode Island, 02917, an indirect
wholly-owned subsidiary of FMR LLC and a bank as defined
in Section 3(a)(6) of the Securities Exchange Act of 1934, is
the beneficial owner of 1,800 shares or 0.005% of the
outstanding Common Stock of the Synaptics Incorporated as a
result of its serving as investment manager of institutional
accounts owning such shares.

	Edward C. Johnson 3d and FMR LLC, through its
control of Pyramis Global Advisors Trust Company, each has
sole dispositive power over 1,800 shares and sole power to
vote or to direct the voting of 0 shares of Common Stock
owned by the institutional accounts managed by PGATC as
reported above.



	SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)
	RULE 13d-1(f)(1)  AGREEMENT

	The undersigned persons, on November 09, 2009,
agree and consent to the joint filing on their behalf of this
Schedule 13G in connection with their beneficial ownership of
the Common Stock of Synaptics Incorporated at October 31,
2009.

	FMR LLC

	By /s/ Scott C. Goebel
	Scott C. Goebel
	Duly authorized under Power of Attorney effective as
of June 1, 2008, by and on behalf of FMR LLC and its direct
and indirect subsidiaries

	Edward C. Johnson 3d

	By /s/ Scott C. Goebel
	Scott C. Goebel
	Duly authorized under Power of Attorney effective as
of June 1, 2008, by and on behalf of Edward C. Johnson 3d

	Fidelity Management & Research Company

	By /s/ Scott C. Goebel
	Scott C. Goebel
	Senior V.P. and General Counsel











SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This website contains forward-looking statements that are subject to the safe harbors created under the Securities Act of 1933, as amended, and the Securities Exchange Act of 1934, as amended. Forward-looking statements give our current expectations and projections relating to our financial condition, results of operations, plans, objectives, future performance and business, and can be identified by the fact that they do not relate strictly to historical or current facts. Such forward-looking statements may include words such as "expect," "anticipate," "intend," "believe," "estimate," "plan," "target," "strategy," "continue," "may," "will," "should," variations of such words, or other words and terms of similar meaning. All forward-looking statements reflect our best judgment and are based on several factors relating to our operations and business environment, all of which are difficult to predict and many of which are beyond our control. Such factors include, but are not limited to, the risks as identified in the "Risk Factors," "Management's Discussion and Analysis of Financial Condition and Results of Operations" and "Business" sections of our Annual Report on Form 10-K for our most recent fiscal year, and other risks as identified from time to time in our Securities and Exchange Commission reports. Forward-looking statements are based on information available to us on the date hereof, and we do not have, and expressly disclaim, any obligation to publicly release any updates or any changes in our expectations, or any change in events, conditions, or circumstances on which any forward-looking statement is based. Our actual results and the timing of certain events could differ materially from the forward-looking statements. These forward-looking statements do not reflect the potential impact of any mergers, acquisitions, or other business combinations that had not been completed as of the date of this filing.