Stock Options, Employee Stock Purchase Plan and Restricted Stock - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2015	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock Option Activity [Abstract]
Outstanding, Beginning balance	6,386	6,386	6,386	9,228	9,727
Outstanding, Beginning balance (in per share)	$ 11.44	$ 11.44	$ 11.44	$ 4.45	$ 4.22
Granted (in shares)		577	1,016	1,475	321
Granted (in per share)		$ 45.91	$ 37.60	$ 28.59	$ 15.76
Exercised (in shares)		(2,519)	(2,519)	(4,226)	(630)
Exercised (in per share)		$ 4.09	$ 4.09	$ 1.91	$ 4.18
Forfeited or expired (in shares)		(106)	(121)	(91)	(190)
Forfeited or expired (in per share)		$ 34.30	$ 34.78	$ 22.56	$ 13.10
Outstanding, Ending balance		4,338	4,762	6,386	9,228
Outstanding, Ending balance (in per share)		$ 19.75	$ 20.33	$ 11.44	$ 4.45
Weighted Average Remaining Contractual Term (Years)		3 years 3 months 22 days	3 years 4 months 28 days	2 years 5 months 23 days
Aggregate Intrinsic Value (in thousands)	$ 132,985	$ 38,007	$ 80,868	$ 158,097
Exercisable, Ending balance (in shares)		2,419	2,510
Exercisable, Ending balance (in per share)		$ 10.88	$ 11.28
Exercisable, contractual term		1 year 7 months 13 days	1 year 5 months 5 days
Exercisable, aggregate intrinsic value	$ 87,991	$ 42,636	$ 65,341