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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator (basic and diluted):
Net income		$ 366,151	$ 283,734	$ 1,024,130	$ 831,489
Denominator:
Weighted-average common shares outstanding - basic		80,593	86,947	81,939	89,641
Effect of stock options	[1]	817	1,078	902	1,228
Weighted-average common shares outstanding - assuming dilution		81,410	88,025	82,841	90,869
Earnings per share - basic		$ 4.54	$ 3.26	$ 12.50	$ 9.28
Earnings per share - assuming dilution		$ 4.50	$ 3.22	$ 12.36	$ 9.15
Antidilutive stock options	[1]	650	784	232	620
Weighted-average exercise price	[1]	$ 264.65	$ 246.65	$ 268.22	$ 258.75

[1] See Note 7 for further information concerning the terms of the Company’s share-based compensation plans.