Net Income per Share - Schedule of Components Used in Diluted and Basic Income Per Common Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Numerator [Abstract]
Net income	$ 72,800	$ 71,487
Denominator [Abstract]
Shares used for basic net income per share (in shares)	178,705	177,899
Effect of dilutive securities:
Convertible senior notes	0	0
Warrants related to issuance of convertible senior notes	0	0
Shares used for diluted net income per share (in shares)	182,038	181,562
Basic net income per share (in dollars per share)	$ 0.41	$ 0.40
Diluted net income per share (in dollars per share)	$ 0.40	$ 0.39
Stock options
Effect of dilutive securities:
Dilutive securities	1,382	1,776
RSUs and deferred stock units
Effect of dilutive securities:
Dilutive securities	1,951	1,887