Earnings Per Share (Computation of Basic and Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Numerator (basic and diluted):
Net income	$ 216,997		$ 186,489		$ 596,504		$ 517,945
Denominator:
Denominator for basic earnings per share - weighted-average shares	103,498		108,307		105,146		110,034
Effect of stock options	1,724	[1]	1,886	[1]	1,799	[1]	1,851	[1]
Denominator for diluted earnings per share - weighted-average shares	105,222		110,193		106,945		111,885
Earnings per share - basic	$ 2.10		$ 1.72		$ 5.67		$ 4.71
Earnings per share - assuming dilution	$ 2.06		$ 1.69		$ 5.58		$ 4.63
Antidilutive stock options	257	[1]	190	[1]	328	[1]	639	[1]
Weighted-average exercise price	$ 141.77	[1]	$ 106.40	[1]	$ 139.13	[1]	$ 98.77	[1]

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