Employee Benefit Plans 401(k) Retirement Plan (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]
401(k) Retirement Plan requisite service period (in months)	3
Eligible age of employees to participate in the 401(k) Retirement Plan (in years)	21
Employer match of employee contributions up to 1%	100.00%
Percentage of eligible compensation matched 100% by employer	1.00%
Employer match of employee contributions over 1% up to 6%	50.00%
Percentage of eligible compensation matched 50% by employer	5.00%
Vesting percentage of employer contributions	100.00%
Vesting period of employer contributions (in years)	2
401(k) Retirement Plan expense	$ 394,000	$ 426,000	$ 411,000