Stock Based Compensation (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010
Summary of option activity
Shares Outstanding, Beginning Balance	1,597,032
Shares, Granted	311,300
Shares, Exercised	40,447	164,341
Shares, Forfeited or expired	185,867
Shares Outstanding, Ending Balance	1,682,018	1,597,032
Shares, Exercisable	1,074,418
Aggregate Intrinsic Value, Outstanding	$ 2,455
Aggregate Intrinsic Value, Exercisable	$ 669
Weighted Average Remaining Contractual Term, Outstanding	5.0
Weighted Average Remaining Contractual Term, Exercisable	3.1
Weighted Average Exercise Price, Outstanding, Beginning Balance	$ 28.91
Weighted Average Exercise Price, Granted	$ 28.64
Weighted Average Exercise Price, Exercised	$ 13.41
Weighted Average Exercise Price, Forfeited or expired	$ 26.04
Weighted Average Exercise Price, Outstanding Ending Balance	$ 29.55	$ 28.91
Weighted Average Exercise Price, Exercisable	$ 31.84