Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income for basic and diluted earnings per share	$ 752,842	$ 693,257	$ 1,337,094	$ 1,022,302
Weighted-average common shares outstanding (shares)	214,694,000	214,819,000	214,882,000	215,663,000
Dilutive effect of stock options, performance share awards and restricted stock awards (shares)	1,130,000	848,000	1,023,000	912,000
Diluted weighted-average shares outstanding (shares)	215,824,000	215,667,000	215,905,000	216,575,000
Basic earnings per share (in dollars per share)	$ 3.51	$ 3.23	$ 6.22	$ 4.74
Diluted earnings per share (in dollars per share)	$ 3.49	$ 3.21	$ 6.19	$ 4.72
Antidilutive securities (shares)	0	0	0	0