Employee Benefit Plans - Pension Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net periodic benefit cost
Employer contributions			$ 2,200	$ 2,300
Pension [Member]
Net periodic benefit cost
Service cost	$ 23	$ 27	68	56
Interest cost	592	569	1,777	1,686
Expected return on plan assets	(612)	(701)	(1,837)	(2,076)
Amortization of prior service cost	25	(34)	76	(102)
Amortization of net (gain) loss	406	433	1,218	1,294
Net periodic benefit cost	$ 434	$ 294	$ 1,302	$ 858