Earnings Per Share - Computation of Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Basic earnings per share:
Net income	$ 178,222	$ 27,658
Weighted-average common shares outstanding (in shares)	430,600	428,117
Basic earnings per share (in dollars per share)	$ 0.41	$ 0.06
Diluted earnings per share:
Net income	$ 178,222	$ 27,658
Shares used in computation:
Weighted-average common shares outstanding (in shares)	430,600	428,117
Employee stock options (in shares)	14,858	9,876
Weighted-average number of shares (in shares)	445,458	437,993
Diluted earnings per share (in dollars per share)	$ 0.40	$ 0.06