Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Net income	$ 41,027	$ 41,886
Convertible debt income adjustments, net of tax	0	604
Net income adjusted for convertible debt as used for diluted earnings per share	$ 41,027	$ 42,490
Net income per share:
Basic (in Dollars per share)	$ 0.33	$ 0.35
Diluted (in Dollars per share)	$ 0.33	$ 0.34
Shares used in computing net income per share:
Weighted average basic shares outstanding (in Shares)	124,421	119,516
Dilutive securities:
Stock option and unvested RSAs (in Shares)	245	1,172
Shares issuable upon conversion of convertible notes (in Shares)	0	4,933
Total dilutive securities (in Shares)	245	6,105
Weighted average diluted shares outstanding (in Shares)	124,666	125,621
Shares subject to stock options omitted from the calculation of income per share as their effect would have been anti-dilutive	4,093	2,430