Equity Compensation (Stock Options Granted, Forfeited, Exercised and Expired) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010	Jun. 30, 2011		Jun. 30, 2010
Equity Compensation
Number of shares outstanding at beginning of period				1,724,791
Number of Shares, Granted	0		0	159,500		305,000
Number of Shares, Forfeited				0
Number of Shares, Exercised	(42,780)		(39,200)	(103,310)		(71,329)
Number of Shares, Expired				0
Number of Shares outstanding at end of period	1,780,981			1,780,981
Number of Shares, Exercisable at end of period	1,334,800			1,334,800
Weighted Average Exercise Price, Outstanding at beginning of period				$ 77.95
Weighted Average Exercise Price, Granted	$ 69.43			$ 69.43
Weighted Average Exercise Price, Forfeited	$ 0.00			$ 0.00
Weighted Average Exercise Price, Exercised	$ 48.23			$ 48.23
Weighted Average Exercise Price, Expired	$ 0.00			$ 0.00
Weighted Average Exercise Price, Outstanding at end of period	$ 78.91			$ 78.91
Weighted Average Exercise Price, Exercisable at end of period	$ 72.13			$ 72.13
Aggregate Exercise Price, Outstanding at beginning of period				$ 134,447
Aggregate Exercise Price, Granted	11,074			11,074
Aggregate Exercise Price, Forfeited	0			0
Aggregate Exercise Price, Exercised	(4,983)			(4,983)
Aggregate Exercise Price, Expired	0			0
Aggregate Exercise Price, Outstanding at end of period	140,538			140,538
Aggregate Exercise Price, Exercisable at end of period	96,273			96,273
Weighted Average Remaining Contractual Term, Outstanding at end of period, years	4.0			4.0
Weighted Average Remaining Contractual Term, Exercisable at end of period, years				3.3
Aggregate Intrinsic Value, Outstanding at end of period	0	[1]		0	[1]
Aggregate Intrinsic Value, Exercisable at end of period	$ 8,162	[1]		$ 8,162	[1]

[1] The aggregate intrinsic value of the stock options was calculated by multiplying the number of shares subject to the options outstanding or exercisable, as applicable, by the closing market price of our common stock on June 30, 2011, and subtracting the applicable aggregate exercise price.