Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Benefits
Components of the net periodic benefit cost
Service cost	$ 0	$ 55
Interest cost	48	1,209
Expected return on plan assets	0	(1,561)
Recognized net actuarial loss	36	370
Benefit cost (income)	84	73
Postretirement Benefits
Components of the net periodic benefit cost
Service cost	213	240
Interest cost	405	406
Amortization of prior service cost	(89)	(136)
Recognized net actuarial loss	235	392
Benefit cost (income)	$ 764	$ 902