Employee Benefit Plans - Reconciliation of Benefit Obligations, Plan Assets and Funded Status (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension plans
Change in benefit obligation:
Benefit obligation at beginning of plan year		$ 42,898
Service cost			$ 2
Interest cost		305	1,228
Actuarial loss		(198)
Benefits paid		(43,005)
Projected benefit obligation at measurement date			42,898
Change in plan assets:
Fair value of plan assets at beginning of plan year	$ 0	41,517
Actual return on plan assets		(1,375)
Company contribution		2,860
Benefits paid		(43,002)
Fair value of plan assets at measurement date	0	0	41,517
Other postretirement benefits
Change in benefit obligation:
Benefit obligation at beginning of plan year	5,551	6,073
Service cost	103	124	121
Interest cost	210	189	195
Actuarial loss	657	(511)
Plan participants' contributions	532	547
Benefits paid	(978)	(871)
Projected benefit obligation at measurement date	$ 6,075	$ 5,551	$ 6,073