Stock Based Compensation Roll Forward Schedule of Stock Option Plan by Shares and Weighted Average Exercise Prices (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Roll Forward of Shares Outstanding [Roll Forward]
Outstanding, Beginning Balance, in shares	482,765
Granted, in shares	75,786	78,425	77,047
Exercised, in shares	97,804
Forfeited, in shares	18,362
Outstanding, Ending Balance, in shares	442,385	482,765
Exercisable at December 31, 2012, in shares	259,150
Vested and Expected to Vest, in shares	183,235
Roll Forward of Shares Outstanding - Weighted Average Exercise Price: [Roll Forward]
Outstanding, Beginning Balance, in Weighted Average Exercise Price,	$ 22.46
Granted, in Weighted Average Exercise Price	$ 24.92
Exercised, in Weighted Average Exercise Price	$ (21.53)
Forfeited, in Weighted Average Exercise Price	$ (23.93)
Outstanding, Ending Balance, in Weighted Average Exercise Price,	$ 23.03	$ 22.46
Exercisable at December 31, 2012, in Weighted Average Exercise Price	$ 22.46
Vested and Expected to Vest, in Weighted Average Exercise Price	$ 23.83
Outstanding at December 31, 2012, Weighted Average Remaining Contractual Life, in years	5 years 11 months 12 days
Exercisable at December 31, 2012, Weighted Average Remaining Contractual Life, in years	4 years 5 months 12 days
Vested and Expected to Vest, Weighted Average Remaining Contractual Life, in years	8 years 0 months 28 days
Outstanding at December 31, 2012, Aggregate Intrinsic Value	$ 849
Exercisable at December 31, 2012, Aggregate Intrinsic Value	645
Vested and Expected to Vest, Aggregate Intrinsic Value	$ 204
Shares Available for Grant at Period End, in shares	37,695