Stock-Based Compensation (Summary Activity Of Employee Stock Options) (Details) (Employee Stock Option [Member], USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2011
Employee Stock Option [Member]
Number of shares, Outstanding at December 31, 2010	13,130,000
Weighted-Average Exercise Price, Outstanding at December 31, 2010	$ 16.93
Number of Shares, Granted	6,264,000
Weighted-Average Exercise Price, Granted	$ 19.65
Number of Shares, Exercised	(1,625,000)
Weighted-Average Exercise Price, Exercised	$ 18.13
Number of Shares, Canceled/forfeited/expired	(1,110,000)
Weighted-Average Exercise Price, Canceled/forfeited/expired	$ 21.92
Number of Shares, Outstanding at September 30, 2011	16,659,000
Weighted-Average Exercise Price, Outstanding at September 30, 2011	$ 17.50
Weighted-Average Remaining Contractual Term, Outstanding at September 30, 2011 (years)	7.64
Aggregate Intrinsic Value, Outstanding at September 30, 2011 (years)	$ 16,873	[1]
Number of Shares, Vested or expected to vest at September 30, 2011	15,135,000
Weighted-Average Exercise Price, Vested or expected to vest at September 30, 2011	$ 17.43
Weighted-Average Remaining Contractual Term, Vested or expected to vest at September 30 , 2011	7.22
Aggregate Intrinsic Value, Vested or expected to vest at September 30, 2011	16,690	[1]
Number of Shares, Exercisable at September, 2011	5,750,000
Weighted-Average Exercise Price, Exercisable at September 30, 2011	$ 14.96
Weighted-Average Remaining Contractual Term, Exercisable at September 30, 2011	4.50
Aggregate Intrinsic Value, Exercisable at September 30, 2011	$ 15,067	[1]
Closing price of Quest Software, Inc.	$ 15.88

[1] These amounts represent the difference between the exercise price and $15.88, the closing price of Quest Software, Inc. stock on September 30, 2011 as reported on the NASDAQ National Market, for all options outstanding that have an exercise price currently below the closing price.