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, 2017	Mar. 31, 2016
Numerator (basic and diluted):
Net income		$ 264,934	$ 255,374
Denominator:
Weighted-average common shares outstanding - basic		92,001	97,140
Effect of stock options	[1]	1,494	1,397
Weighted-average common shares outstanding - assuming dilution		93,495	98,537
Earnings per share - basic		$ 2.88	$ 2.63
Earnings per share - assuming dilution		$ 2.83	$ 2.59
Antidilutive stock options	[1]	478	268
Weighted-average exercise price	[1]	$ 266.71	$ 256.19

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