Earnings Per Share (Computation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator (basic and diluted):
Net income		$ 283,734	$ 278,493	$ 831,489	$ 791,661
Denominator:
Weighted-average common shares outstanding - basic		86,947	94,891	89,641	95,994
Effect of stock options	[1]	1,078	1,229	1,228	1,315
Weighted-average common shares outstanding - assuming dilution		88,025	96,120	90,869	97,309
Earnings per share - basic		$ 3.26	$ 2.93	$ 9.28	$ 8.25
Earnings per share - assuming dilution		$ 3.22	$ 2.90	$ 9.15	$ 8.14
Antidilutive stock options	[1]	784	271	620	319
Weighted-average exercise price	[1]	$ 246.65	$ 267.66	$ 258.75	$ 264.88

[1] See Note 6 for further information concerning the terms of the Company’s share-based compensation plans.