Employee Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Settlements			$ 500		$ 1,400
Components of net periodic benefit cost:
Interest cost	$ 0		204	$ 0	612
Actuarial loss	0		184	0	553
Settlement charge	0		546	3,325	3,909
Net periodic (income) expense	0		934	3,325	5,074
Postretirement Benefit Plans
Components of net periodic benefit cost:
Service cost	24		98	71	294
Interest cost	52		117	170	350
Expected long-term return on assets	(68)		(114)	(248)	(343)
Prior service cost amortization	(113)		0	(351)	0
Settlement charge	0		0	45	0
Curtailment gain	0	$ (800)	0	(816)	0
Net periodic (income) expense	$ (105)		$ 101	$ (1,129)	$ 301