Basic and Diluted Net Income Per Share - Computation of Basic and Diluted Net Income Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Numerator:
Net income	$ 4,147	$ 18,275
Denominator:
Weighted average common shares - basic (in shares)	76,205	74,754
Weighted average common shares - diluted (in shares)	79,231	78,064
Net income per share:
Basic (in dollars per share)	$ 0.05	$ 0.24
Diluted (in dollars per share)	$ 0.05	$ 0.23
Potentially dilutive securities excluded from net income per share - diluted because their effect is anti-dilutive (in shares)	43	658
Employee Stock Option [Member]
Denominator:
Effect of Dilutive Securities (in shares)	2,806	3,306
Employee Stock [Member]
Denominator:
Effect of Dilutive Securities (in shares)	95	4
Restricted Stock Units (RSUs) [Member]
Denominator:
Effect of Dilutive Securities (in shares)	125	0