Deferred Compensation Plan Deferred Compensation Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Compensation Plan [Abstract]
Maximum Deferral Percentage of Base Compensation under Deferred Compensation Plan	50.00%
Maximum Deferral Percentage of Bonus Compensation under Deferred Compensation Plan	100.00%
Contributions by Employer under Deferred Compensation Plan	$ 100	$ 300	$ 400
Employer match under Deferred Compensation Plan, Percent	50.00%
Employee Contribution Maximum Percent of Compensation under Deferred Compensation Plan	6.00%
Discretionary Contribution under Deferred Compensation Plan	$ 0
Deferred compensation	$ 11,323	$ 11,394