Employee Retirement Plans - Expected Benefit Payments (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Expected benefit payments
Voluntary contribution			$ 7,000
Conjunction with the termination	$ 464
Pension plan
Expected benefit payments
Pension funding contributions made		$ 460	$ 7,047
Pension plan | Minimum
Expected benefit payments
Pension funding contributions made		$ 0