Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Employee Benefit Plans [Line Items]
Target asset allocation, fixed income investments, percentage					100.00%	49.00%
Amount of unamortized losses in other comprehensive income			$ 54,400
Additional company contributions to settle pension obligation			6,900
Pension Benefits
Components of the net periodic benefit cost
Service cost	$ 59	$ 45	177	$ 135
Interest cost	45	1,193	136	3,580
Expected return on plan assets	0	(1,903)	0	(5,711)
Recognized net actuarial loss	379	234	1,137	701
Benefit cost (income)	483	(431)	1,450	(1,295)
Postretirement Benefits
Components of the net periodic benefit cost
Service cost	225	173	675	516
Interest cost	396	377	1,188	1,133
Amortization of prior service cost	(136)	(136)	(408)	(408)
Recognized net actuarial loss	379	203	1,138	609
Benefit cost (income)	$ 864	$ 617	$ 2,593	$ 1,850