Employee Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Feb. 28, 2013	Feb. 01, 1999
401(k) Plan
Employee Benefit Plans:
Number of common stock shares reserved for issuance (in shares)					150,000
Number of additional common stock shares reserved for issuance (in shares)				500,000
Employer match of employee contributions of first 3% of eligible compensation (as a percent)	100.00%
Percentage of eligible compensation, matched 100% by employer (as a percent)	3.00%
Employer match of employee contributions of next 2% of eligible compensation (as a percent)	50.00%
Percentage of eligible compensation, matched 50% by employer (as a percent)	2.00%
Employer contribution	$ 3,422	$ 3,481	$ 3,384
Deferred Compensation Plans
Employee Benefit Plans:
Employer contribution	$ 813	$ 1,069	$ 1,032