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, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Numerator (basic and diluted):
Net income		$ 233,508	$ 205,647	$ 446,372	$ 379,507
Denominator:
Denominator for basic earnings per share - weighted-average shares		100,547	105,772	101,078	105,982
Effect of stock options	[1]	1,562	1,784	1,606	1,835
Denominator for diluted earnings per share - weighted-average shares		102,109	107,556	102,684	107,817
Earnings per share - basic		$ 2.32	$ 1.94	$ 4.42	$ 3.58
Earnings per share - assuming dilution		$ 2.29	$ 1.91	$ 4.35	$ 3.52
Antidilutive stock options	[1]	226	305	312	336
Weighted-average exercise price	[1]	$ 206.72	$ 137.82	$ 200.65	$ 137.35

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