Stock-Based Compensation (Summary Of Employee Stock Options Activity) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 Y
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Closing price of Quest Software, Inc.	$ 23.27
Employee Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, Outstanding at December 31, 2011	15,779
Number of Shares, Granted	133
Number of Shares, Exercised	(863)
Number of Shares, Canceled/forfeited/expired	(427)
Number of Shares, Outstanding at March 31, 2012	14,622
Number of Shares, Vested or expected to vest at March 31, 2012	13,502
Number of Shares, Exercisable at March 31, 2012	5,989
Weighted-Average Exercise Price, Outstanding at December 31, 2011	$ 17.26
Weighted-Average Exercise Price, Granted	$ 19.36
Weighted-Average Exercise Price, Exercised	$ 17.27
Weighted-Average Exercise Price, Canceled/forfeited/expired	$ 18.25
Weighted-Average Exercise Price, Outstanding at March 31, 2012	$ 17.24
Weighted-Average Exercise Price, Vested or expected to vest at March 31, 2012	$ 17.19
Weighted-Average Exercise Price, Exercisable at March 31, 2012	$ 15.42
Weighted-Average Remaining Contractual Term (in years), Outstanding at March 31, 2012	7.22
Weighted-Average Remaining Contractual Term (in years), Vested or expected to vest at March 31, 2012	7.07
Weighted-Average Remaining Contractual Term (in years), Exercisable at March 31, 2012	5.00
Aggregate Intrinsic Value, Outstanding at March 31, 2012	$ 93,754	[1]
Aggregate Intrinsic Value, Vested or expected to vest at March 31, 2012	87,229	[1]
Aggregate Intrinsic Value, Exercisable at March 31, 2012	$ 48,501	[1]

[1] These amounts represent the difference between the exercise price and $23.27, the closing price of Quest Software, Inc. stock on March 31, 2012 as reported on the NASDAQ National Market, for all options outstanding that have an exercise price currently below the closing price.