Earnings Per Share - Calculation of EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Basic earnings per share:
Net income	$ 665,244	$ 402,835	$ 1,279,946	$ 1,077,308
Weighted-average common shares outstanding (in shares)	438,090	435,809	437,547	435,033
Basic earnings per share (in dollars per share)	$ 1.52	$ 0.92	$ 2.93	$ 2.48
Diluted earnings per share:
Net income	$ 665,244	$ 402,835	$ 1,279,946	$ 1,077,308
Shares used in computation:
Weighted-average common shares outstanding (in shares)	438,090	435,809	437,547	435,033
Employee stock options (in shares)	13,462	16,110	14,349	16,250
Weighted-average number of shares (in shares)	451,552	451,919	451,896	451,283
Diluted earnings per share (in dollars per share)	$ 1.47	$ 0.89	$ 2.83	$ 2.39