Employee Retirement Plans - FV Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of the fair value measurements using significant unobservable inputs (Level 3)
Fair value of plan assets at beginning of year	$ 38,053
Fair value of plan assets at end of year		$ 38,053
Level 3
Reconciliation of the fair value measurements using significant unobservable inputs (Level 3)
Fair value of plan assets at beginning of year	656	2,026
Deposits		213
Actual return on plan assets held at reporting date	30	136
Withdrawals and transfers	(686)	(1,719)
Fair value of plan assets at end of year		656
Pension plan
Reconciliation of the fair value measurements using significant unobservable inputs (Level 3)
Fair value of plan assets at beginning of year	$ 38,053	33,903
Fair value of plan assets at end of year		$ 38,053