Employee Retirement Plans - FV Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of the fair value measurements using significant unobservable inputs (Level 3)
Fair value of plan assets at beginning of year	$ 33,903
Fair value of plan assets at end of year	38,053	$ 33,903
Level 3
Reconciliation of the fair value measurements using significant unobservable inputs (Level 3)
Fair value of plan assets at beginning of year	2,026	1,748
Deposits	213	100
Actual return on plan assets held at reporting date	136	142
Withdrawals and transfers	(1,719)	36
Fair value of plan assets at end of year	656	2,026
Pension plan
Reconciliation of the fair value measurements using significant unobservable inputs (Level 3)
Fair value of plan assets at beginning of year	33,903	29,223
Fair value of plan assets at end of year	$ 38,053	$ 33,903