Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Defined pension plan benefits
Components of net periodic benefit cost
Service cost (benefit) – benefits earned during the year	$ 48	$ (2)	$ 55	$ 14
Interest cost on projected benefit obligations	450	454	905	900
Expected return on plan assets	(538)	(532)	(1,087)	(1,075)
Amortization of prior service cost	0	0	0	0
Amortization of net loss	154	163	311	354
Net periodic benefit cost	114	83	184	193
Other postretirement benefits
Components of net periodic benefit cost
Service cost (benefit) – benefits earned during the year	33	34	69	74
Interest cost on projected benefit obligations	65	60	129	126
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	(7)	13	(13)	26
Amortization of net loss	0	0	0	0
Net periodic benefit cost	$ 91	$ 107	$ 185	$ 226