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				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Numerator (basic and diluted):
Net income	$ 205,647		$ 177,127		$ 379,507		$ 331,456
Denominator:
Denominator for basic earnings per share - weighted-average shares	105,772		110,278		105,982		110,914
Effect of stock options	1,784	[1]	1,801	[1]	1,835	[1]	1,822	[1]
Denominator for diluted earnings per share - weighted-average shares	107,556		112,079		107,817		112,736
Earnings per share - basic	$ 1.94		$ 1.61		$ 3.58		$ 2.99
Earnings per share - assuming dilution	$ 1.91		$ 1.58		$ 3.52		$ 2.94
Antidilutive stock options	305	[1]	784	[1]	336	[1]	1,182	[1]
Weighted-average exercise price	$ 137.82	[1]	$ 96.38	[1]	$ 137.35	[1]	$ 93.57	[1]

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