Note 12 - Stockholders' Equity (Details) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended		1 Months Ended	12 Months Ended						0 Months Ended				1 Months Ended	4 Months Ended	12 Months Ended		14 Months Ended	12 Months Ended
	Aug. 31, 2013	May 14, 2013	Apr. 30, 2013	Aug. 31, 2013		Aug. 31, 2012		Aug. 31, 2011	Aug. 31, 2010	Apr. 08, 2013 Restricted Stock [Member]	Apr. 14, 2011 Restricted Stock [Member]	Nov. 08, 2010 Restricted Stock [Member]	Feb. 09, 2010 Restricted Stock [Member]	Jan. 27, 2011 Restricted Stock [Member]	Aug. 31, 2012 Restricted Stock [Member]	Aug. 31, 2013 Restricted Stock [Member]	Aug. 31, 2012 Restricted Stock [Member]	Jul. 31, 2011 Restricted Stock [Member]	Aug. 31, 2013 Share Repurchase Program [Member]
Note 12 - Stockholders' Equity (Details) [Line Items]
Preferred Stock, Shares Authorized	10,000,000			10,000,000		10,000,000
Preferred Stock, Par or Stated Value Per Share (in Dollars per share)	$ 0.01			$ 0.01		$ 0.01
Preferred Stock, Shares Issued	0			0		0
Preferred Stock, Shares Outstanding	0			0		0
Common Stock, Shares Authorized	150,000,000			150,000,000		150,000,000
Common Stock, Par or Stated Value Per Share (in Dollars per share)	$ 0.01			$ 0.01		$ 0.01
Common Stock, Shares, Issued	48,110,740			48,110,740		45,599,754
Treasury Stock, Shares	4,786,330			4,786,330		1,320,540
Common Stock, Shares, Outstanding	43,324,410			43,324,410		44,279,214		45,055,000	46,024,000
Stock Repurchase Program, Authorized Amount (in Dollars)		$ 200
Stock Repurchased During Period, Shares				3,414,000		1,644,000		2,252,000											3,400,000
Stock Repurchased During Period, Value (in Dollars)						152.7													327.3
Stock Repurchase Program, Remaining Authorized Repurchase Amount (in Dollars)	62.4
Shares Paid for Tax Withholding for Share Based Compensation				50,828												50,828
Payments Related to Tax Withholding for Share-based Compensation (in Dollars)				$ 4.7
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period			131,702	132,000		0		154,000		131,702	30,090	117,723	55,572	366		131,702	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period				150,000	[1]	14,000	[2]	0							14,258	149,741	14,258	21,102

[1] Of the total 149,741 restricted stock awards that vested during fiscal 2013, 87,758 related to awards granted on October 23, 2009. These restricted stock awards cliff vested 60% after three years (on October 23, 2012) and the remaining 40% will vest after five years (on October 23, 2014). An additional 55,572 awards that vested in fiscal 2013 related to awards granted on February 9, 2010 at a price of $63.09. These restricted stock awards cliff vested 100% after three years (on February 9, 2013). The remaining 6,411 restricted stock awards that vested were previously granted between June 2010 and July 2011 and vesting occured when certain ASV targets were met in fiscal 2013.

[2] * Between June 2010 and July 2011, FactSet granted 21,102 restricted stock units which entitled the holder to shares of common stock as the awards vest. A restricted stock unit is a promise to deliver shares to the employee at a future date if certain vesting conditions are met. These restricted stock units are performance-based and cliff vest 25% when certain ASV targets are met. Of the total 21,102 units granted, 14,258 units vested during the fourth quarter of fiscal 2012 because FactSet achieved three of the four ASV growth targets.