Stock Based Compensation (Summary of Company's Outstanding Restricted Stock) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Vests, Number of Shares	336,919	[1]	227,094	[1]	78,826	[1]
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares outstanding, Number of Shares, Beginning Balance	58,661
Shares outstanding, Weighted-Average Grant-Date Fair Value, Beginning Balance	52.77
Grants, Number of Shares	0
Grants, Weighted Average Exercise Price	0.00
Vests, Number of Shares	50,538
Vests, Weighted-Average Grant-Date Fair Value	52.44
Forfeitures, Number of Shares	438
Forfeitures, Weighted-Average Grant-Date Fair Value	61.33
Shares outstanding, Number of Shares, Ending Balance	7,685
Shares outstanding, Weighted-Average Grant-Date Fair Value, Ending Balance	54.44

[1] Vested restricted stock and restricted stock units shown net of shares retired to cover participant tax liability