Summary of Option Activity (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Dec. 31, 2014
Shares
Outstanding at October 1, 2014	2,089
Granted	493
Exercised	(217)
Forfeited	(35)
Outstanding at December 31, 2014	2,330
Options exercisable at December 31, 2014	1,103
Vested and expected to vest at December 31, 2014	2,151
Weighted-average Exercise Price
Outstanding at October 1, 2014 (in dollars per share)	$ 36.24
Granted (in dollars per share)	$ 72.06
Exercised (in dollars per share)	$ 30.92
Forfeited (in dollars per share)	$ 39.49
Outstanding at December 31, 2014 (in dollars per share)	$ 44.27
Options exercisable at December 31, 2014 (in dollars per share)	$ 33.79
Vested and expected to vest at December 31, 2014 (in dollars per share)	$ 43.17
Weighted-average Remaining Contractual Term
Outstanding at December 31, 2014	4 years 8 months 20 days
Options exercisable at December 31, 2014	3 years 9 months 20 days
Vested and expected to vest at December 31, 2014	4 years 8 months 4 days
Aggregate Intrinsic Value
Outstanding at December 31, 2014	$ 65,330
Options exercisable at December 31, 2014	42,477
Vested and expected to vest at December 31, 2014	$ 62,664