Earnings Per Share - Computation of Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Basic earnings per share:
Net income	$ 344,052	$ 290,124
Weighted-average common shares outstanding (in shares)	436,947	434,174
Basic earnings per share (in dollars per share)	$ 0.79	$ 0.67
Diluted earnings per share:
Net income	$ 344,052	$ 290,124
Shares used in computation:
Weighted-average common shares outstanding (in shares)	436,947	434,174
Employee stock options (in shares)	14,975	16,185
Weighted-average number of shares (in shares)	451,922	450,359
Diluted earnings per share (in dollars per share)	$ 0.76	$ 0.64