Stock-Based Compensation (Schedule of Other Stock-Based Awards Activity) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Time-Vested Restricted Share Units [Member]
Nonvested at January 1, 2012, Shares	276
Granted, Shares	270
Vested, Shares	(198)
Forfeited, Shares	(24)
Nonvested at December 31, 2012, Shares	324
Nonvested at January 1, 2012, Weighted-Average Grant-Date Fair Value	$ 61.07
Granted, Weighted-Average Grant-Date Fair Value	$ 77.89
Vested, Weighted-Average Grant-Date Fair Value	$ 60.23
Forfeited, Weighted-Average Grant-Date Fair Value	$ 65.62
Nonvested at December 31, 2012, Weighted-Average Grant-Date Fair Value	$ 75.24
Performance-Based Restricted Share Units [Member]
Nonvested at January 1, 2012, Shares	2,398
Granted, Shares	1,127
Vested, Shares	(1,143)
Forfeited, Shares	(195)
Nonvested at December 31, 2012, Shares	2,187
Nonvested at January 1, 2012, Weighted-Average Grant-Date Fair Value	$ 59.08
Granted, Weighted-Average Grant-Date Fair Value	$ 66.57
Vested, Weighted-Average Grant-Date Fair Value	$ 49.53
Forfeited, Weighted-Average Grant-Date Fair Value	$ 65.02
Nonvested at December 31, 2012, Weighted-Average Grant-Date Fair Value	$ 67.41