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, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator [Abstract]
Net income (in dollars)	$ 73,635	$ 67,200	$ 148,493	$ 144,946
Denominator [Abstract]
Shares used for basic net income per share	175,499	178,682	175,951	178,614
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	176,420	180,738	176,980	180,782
Basic net income per share (in dollars per share)	$ 0.42	$ 0.38	$ 0.84	$ 0.81
Diluted net income per share (in dollars per share)	$ 0.42	$ 0.37	$ 0.84	$ 0.80
Stock options
Effect of dilutive securities:
Dilutive securities (in shares)	396	912	400	954
RSUs and deferred stock units
Effect of dilutive securities:
Dilutive securities (in shares)	525	1,144	629	1,214