Earnings Per Share (Computation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Numerator (basic and diluted):
Net income		$ 321,152	$ 304,906
Denominator:
Weighted-average common shares outstanding - basic		78,484	83,530
Effect of stock options	[1]	813	993
Weighted-average common shares outstanding - assuming dilution		79,297	84,523
Earnings per share - basic		$ 4.09	$ 3.65
Earnings per share - assuming dilution		$ 4.05	$ 3.61
Antidilutive stock options	[1]	176	761
Weighted-average exercise price	[1]	$ 347.98	$ 259.28

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