Employee Benefit Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
Investment
Assets contributed to 401(k) Plan				$ 7,900
Restricted investments	$ 3,432	$ 4,469
401(k) Plan distribution period (in years)	3 years
Compensation expense for assets allocated to participants	$ 1,100	1,200	$ 1,400
Realized gain (loss)		10,750	795
Maximum
Investment
Realized gain (loss)	$ (100)	$ 100	$ (100)