Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost — benefits earned during the period	$ 134	$ 147	$ 267	$ 294
Interest cost on projected benefit obligation	1,215	1,124	2,430	2,246
Expected return on assets	(1,219)	(1,393)	(2,437)	(2,786)
Amortization of prior service cost	0	0	0	0
Amortization of net loss (gain)	501	451	1,002	903
Net expense	631	329	1,262	657
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost — benefits earned during the period	1	0	1	1
Interest cost on projected benefit obligation	87	82	173	164
Expected return on assets	0	0	0	0
Amortization of prior service cost	1	0	2	0
Amortization of net loss (gain)	(10)	(10)	(54)	(20)
Net expense	$ 79	$ 72	$ 122	$ 145