Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension Plans
Components of net periodic benefit cost:
Service cost	$ 0	$ 1,902	$ 0	$ 5,157
Interest cost	204	1,157	612	3,974
Expected long-term return on assets	0	(1,157)	0	(4,067)
Actuarial gain (loss)	184	1,296	553	4,115
Prior service cost amortization	0	63	0	177
Settlement charge	546	370	3,909	4,043
Net periodic (income) expense	934	3,631	5,074	13,399
Postretirement Benefit Plans
Components of net periodic benefit cost:
Service cost	98	87	294	206
Interest cost	117	137	350	587
Expected long-term return on assets	(114)	(246)	(343)	(1,016)
Actuarial gain (loss)	0	(151)	0	(572)
Transition amortization	0	9	0	39
Net periodic (income) expense	$ 101	$ (164)	$ 301	$ (756)