Net Income per Share - Schedule of Components Used in Diluted and Basic Income Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator [Abstract]
Net income (in dollars)	$ 60,512	$ 76,000	$ 199,214	$ 224,493
Denominator [Abstract]
Shares used for basic net income per share	170,976	174,429	172,269	175,444
Effect of dilutive securities:
Convertible senior notes (in shares)	0	0	0	0
Warrants related to issuance of convertible senior notes (in shares)	0	0	0	0
Shares used for diluted net income per share	171,505	175,617	173,371	176,525
Basic net income per share (in dollars per share)	$ 0.35	$ 0.44	$ 1.16	$ 1.28
Diluted net income per share (in dollars per share)	$ 0.35	$ 0.43	$ 1.15	$ 1.27
Stock options
Effect of dilutive securities:
Dilutive securities (in shares)	150	341	279	380
RSUs and deferred stock units
Effect of dilutive securities:
Dilutive securities (in shares)	379	847	823	701