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		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Numerator [Abstract]
Net income (in dollars)	$ 72,886	$ 61,895	$ 145,686	$ 133,382
Denominator [Abstract]
Shares used for basic net income per share	178,081	177,891	178,393	177,895
Effect of dilutive securities:
Convertible senior notes	0	0	0	0
Warrants related to issuance of convertible senior notes	0	0	0	0
Shares used for diluted net income per share	180,841	181,388	181,439	181,475
Basic net income per share (in dollars per share)	$ 0.41	$ 0.35	$ 0.82	$ 0.75
Diluted net income per share (in dollars per share)	$ 0.40	$ 0.34	$ 0.80	$ 0.73
Stock options
Effect of dilutive securities:
Dilutive securities	1,242	1,724	1,312	1,750
RSUs and deferred stock units
Effect of dilutive securities:
Dilutive securities	1,518	1,773	1,734	1,830