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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator [Abstract]
Net income (in dollars)	$ 57,772	$ 73,635	$ 138,702	$ 148,493
Denominator [Abstract]
Shares used for basic net income per share	172,674	175,499	172,916	175,951
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	173,439	176,420	174,305	176,980
Basic net income per share (in dollars per share)	$ 0.33	$ 0.42	$ 0.80	$ 0.84
Diluted net income per share (in dollars per share)	$ 0.33	$ 0.42	$ 0.80	$ 0.84
Stock options
Effect of dilutive securities:
Dilutive securities (in shares)	329	396	344	400
RSUs and deferred stock units
Effect of dilutive securities:
Dilutive securities (in shares)	436	525	1,045	629