Employee Benefit Plans - Change in Benefit Obligation and Fair Value (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in Benefit Obligation
Benefit obligation at beginning of year	$ 31,050	$ 37,482	$ 36,626
Service cost	1,776	1,508	2,323
Interest cost	1,172	1,097	1,498
Actuarial (gain) loss	(3,165)	5,156	(2,846)
Benefits paid	(1,056)	(1,204)	(934)
Curtailments	0	(4,346)	0
Plan amendments	0	(8,643)	815
Benefit obligation at end of year	29,777	31,050	37,482
Change in Plan Assets
Fair value of plan assets at end of year	0	0	0
Funded status at end of year	$ (29,777)	$ (31,050)	$ (37,482)