Common Stock and Stock-based Compensation (Details 1) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of company's stock option activity
Number of options outstanding, Beginning balance	113
Exercise of stock options	(16)	(53)	(154)
Cancelled stock options	(1)
Number of options outstanding, Ending balance	96	113
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Number of options outstanding, Weighted average Exercise Price Per Share, Beginning of Period	$ 15.03
Exercised, Weighted average exercise price per share	$ 9.75
Cancelled, Weighted average exercise price per share	$ 7.27
Number of options outstanding, Weighted Average Exercise Price Per Share, Ending of Period	$ 15.98	$ 15.03
Number of options, vested and expected to vest	96
Number of options outstanding, exercisable	96
Number of options, vested and expected to vest, Weighted Average Exercise Price Per Share	$ 15.98
Number of options outstanding, exercisable, Weighted Average Exercise Price Per Share	$ 15.98
Number of options, outstanding, Aggregate Intrinsic Value	$ 943,000
Number of options, vested and expected to vest, Aggregate Intrinsic Value	943,000
Number of options, Exercisable, Aggregate Intrinsic Value	$ 943,000
Number of options, outstanding, Weighted Average Remaining Term (Years)	1 year 4 months 24 days
Number of options, vested and expected to vest, Weighted Average Remaining Term (Years)	1 year 4 months 24 days
Number of options, Exercisable, Weighted Average Remaining Term (Years)	1 year 4 months 24 days