Common Stock and Stock-based Compensation (Details 4) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Directors' Deferred Compensation Plan, Weighted Average Grant Date Fair Value
Weighted average grant date fair value, distributed in period	$ (9.75)
Deferred Directors Compensation Plan [Member]
Summary of stock activity for the directors deferred compensation plan
Number of options outstanding, Beginning Balance	101
Number of shares, Granted in Period	8
Number of shares distributed in period	(6)
Number of options outstanding, Ending Balance	103	101
Directors' Deferred Compensation Plan, Weighted Average Grant Date Fair Value
Restricted stock Options, Weighted Average Grant Date Fair Value, Beginning balance	$ 26.42
Number of restricted stock Options, Granted in Period, Weighted Average Grant Date Fair Value	$ 23.10	$ 38.00	$ 25.13
Weighted average grant date fair value, distributed in period	$ (26.40)
Restricted stock Options, Weighted Average Grant Date Fair Value, Ending balance	$ 38.68	$ 26.42