Employee Stock Purchase Plan Stock Options and Warrants - Options Outstanding (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise, minimum	$ 7.79
Range of Exercise, maximum	$ 17.34
Options Outstanding, Number Outstanding	3,535
Options Exercisable, Number Exercisable	2,521
$7.65 - $9.70 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise, minimum	$ 7.79
Range of Exercise, maximum	$ 11.05
Options Outstanding, Number Outstanding	932
Options Outstanding, Weighted Average Remaining Contractual Life	1 year 8 months 27 days
Options Outstanding, Weighted Average Exercise Price	$ 9.83
Options Exercisable, Number Exercisable	932
Options Exercisable, Weighted Average Exercise Price	$ 9.83
$9.71 - $11.53 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise, minimum	$ 11.41
Range of Exercise, maximum	$ 12.02
Options Outstanding, Number Outstanding	922
Options Outstanding, Weighted Average Remaining Contractual Life	2 years 2 months 27 days
Options Outstanding, Weighted Average Exercise Price	$ 11.69
Options Exercisable, Number Exercisable	812
Options Exercisable, Weighted Average Exercise Price	$ 11.71
$12.02 - $13.75 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise, minimum	$ 12.10
Range of Exercise, maximum	$ 13.75
Options Outstanding, Number Outstanding	1,042
Options Outstanding, Weighted Average Remaining Contractual Life	5 years 7 months 2 days
Options Outstanding, Weighted Average Exercise Price	$ 13.59
Options Exercisable, Number Exercisable	206
Options Exercisable, Weighted Average Exercise Price	$ 13.63
$13.82 - $17.34 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise, minimum	$ 13.82
Range of Exercise, maximum	$ 17.34
Options Outstanding, Number Outstanding	639
Options Outstanding, Weighted Average Remaining Contractual Life	1 year 10 months 24 days
Options Outstanding, Weighted Average Exercise Price	$ 16.05
Options Exercisable, Number Exercisable	571
Options Exercisable, Weighted Average Exercise Price	$ 16.30