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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Numerator (basic and diluted):
Net income		$ 266,268	$ 216,997	$ 712,640	$ 596,504
Denominator:
Weighted-average common shares outstanding - basic		99,270	103,498	100,468	105,146
Effect of stock options	[1]	1,500	1,724	1,573	1,799
Weighted-average common shares outstanding - assuming dilution		100,770	105,222	102,041	106,945
Earnings per share - basic		$ 2.68	$ 2.10	$ 7.09	$ 5.67
Earnings per share - assuming dilution		$ 2.64	$ 2.06	$ 6.98	$ 5.58
Antidilutive stock options	[1]	176	257	256	328
Weighted-average exercise price	[1]	$ 218.21	$ 141.77	$ 210.49	$ 139.13

[1] See Note 6 for further discussion on the terms of the Company's share-based compensation plans.