Employee Benefit Plans - Pension and Postretirement Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net periodic benefit cost
Service cost	$ 82	$ 8
Interest cost	2,319	2,288
Pension And Postretirement [Member]
Net periodic benefit cost
Service cost	82	8	$ 11
Interest cost	2,351	2,288	2,667
Expected return on plan assets	(1,862)	(2,392)	(2,623)
Amortization of prior service cost	139	(134)	(141)
Amortization of net (gain) loss		2,063	891
Net periodic benefit cost	$ 710	$ 1,833	$ 805