Stock-Based Awards - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Stock Options Outstanding, Shares
Shares outstanding, beginning of period (in shares)	6,041
Granted (in shares)	0
Exercised (in shares)	(413)
Forfeited (in shares)	(334)
Shares outstanding, period end (in shares)	5,294	6,041
Stock Options Outstanding, Weighted Average Exercise Price
Weighted average exercise price, outstanding, beginning of period (in usd per share)	$ 32.01
Weighted average exercise price, granted (in usd per share)	0.00
Weighted average exercise price, exercised (in usd per share)	16.38
Weighted average exercise price, forfeited (in usd per share)	35.71
Weighted average exercise price, outstanding, period end (in usd per share)	$ 32.99	$ 32.01
Stock Options, Additional Disclosures
Weighted average remaining contractual term, outstanding	5 years 4 months 5 days	6 years 2 months 12 days
Aggregate intrinsic value, outstanding	$ 40,122	$ 74,989
Exercisable (in shares)	4,934
Weighted average exercise price, exercisable (in usd per share)	$ 32.60
Weighted average remaining contractual term, exercisable	5 years 2 months 19 days
Aggregate intrinsic value, exercisable	$ 39,951
Stock Options Vested and Expected to Vest
Shares vested and expected to vest (in shares)	5,280
Weighted average exercise price, vested and expected (in usd per share)	$ 32.98
Weighted average remaining contractual term, vested and expected to vest	5 years 4 months 3 days
Aggregate intrinsic value, vested and expected to vest	$ 40,113
Closing stock price (usd per share)	$ 35.33	$ 42.31