Earnings Per Share (Computation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator (basic and diluted):
Net income		$ 353,681	$ 353,073	$ 674,833	$ 657,979
Denominator:
Weighted-average common shares outstanding - basic		77,613	81,733	78,047	82,624
Effect of stock options	[1]	799	803	807	806
Weighted-average common shares outstanding - assuming dilution		78,412	82,536	78,854	83,430
Earnings per share - basic		$ 4.56	$ 4.32	$ 8.65	$ 7.96
Earnings per share - assuming dilution		$ 4.51	$ 4.28	$ 8.56	$ 7.89
Antidilutive stock options	[1]	184	693	188	714
Weighted-average exercise price	[1]	$ 357.18	$ 261.11	$ 357.33	$ 260.39

[1] See Note 8 for further information concerning the terms of the Company’s share-based compensation plans.