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
Components of the net periodic benefit cost
Service cost	$ 0	$ 59	$ 0	$ 177
Interest cost	49	45	145	136
Recognized net actuarial loss	36	379	109	1,137
Benefit cost (income)	85	483	254	1,450
Postretirement Benefits
Components of the net periodic benefit cost
Service cost	190	225	570	675
Interest cost	387	396	1,162	1,188
Amortization of prior service cost	(88)	(136)	(266)	(408)
Recognized net actuarial loss	192	379	576	1,138
Benefit cost (income)	$ 681	$ 864	$ 2,042	$ 2,593