Stock-based Compensation (Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding and Exercisable) (Details) (Options, USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended
	Mar. 31, 2014
Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at September 30, 2013	5,351
Granted	1,245
Exercised	(916)
Cancelled/Expired	(37)
Outstanding at March 31, 2014	5,643
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding at September 30, 2013	$ 7.51
Granted	$ 11.06
Exercised	$ 6.70
Cancelled/Expired	$ 10.90
Outstanding at March 31, 2014	$ 8.40
Aggregate Intrinsic Value, options exercised	$ 5,287
Weighted-Average Remaining Contractual Term in Years, Outstanding at March 31, 2014 (years)	4 years 5 months 12 days
Aggregate Intrinsic Value, Outstanding at March 31, 2014	40,321
Number of Shares, Exercisable at March 31, 2014 (shares)	2,804
Weighted-Average Exercise Price, Exercisable at March 31, 2014	$ 6.61
Weighted-Average Remaining Contractual Term in Years, Exercisable at March 31, 2014 (years)	3 years 1 month 21 days
Aggregate Intrinsic Value, Exercisable at March 31, 2014	25,064
Number of Shares, Vested and expected to vest after March 31, 2014 (shares)	5,494
Weighted-Average Exercise Price, Vested and expected to vest after March 31, 2014	$ 8.35
Weighted-Average Remaining Contractual Term in Years, Vested and expected to vest after March 31, 2014 (years)	4 years 4 months 28 days
Aggregate Intrinsic Value, Vested and expected to vest after March 31, 2014	$ 39,555