Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost — benefits earned during the period	$ 137	$ 133	$ 411	$ 398
Interest cost on projected benefit obligation	1,355	1,205	4,065	3,803
Expected return on assets	(1,519)	(1,814)	(4,557)	(5,627)
Settlement loss	0	0	0	1,607
Amortization of net loss (gain)	464	254	1,392	823
Net expense (income)	437	(222)	1,311	1,004
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost — benefits earned during the period	1	2	3	6
Interest cost on projected benefit obligation	97	93	291	278
Expected return on assets	0	0	0	0
Settlement loss	0	0	0	0
Amortization of net loss (gain)	(19)	(24)	(57)	(73)
Net expense (income)	$ 79	$ 71	$ 237	$ 211