Retirement and Postretirement Plans - Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 0	$ 170	$ 170
Interest cost	22,581	28,147	3,312
Expected return on plan assets	(30,100)	(33,973)	(3,509)
Settlement loss recognized	0	7,744	0
Amortization of net loss	808	1,098	35
Net periodic benefit cost (benefit)	(6,711)	3,186	8
Other Pension Plan, Postretirement or Supplemental Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	61	81	11
Interest cost	829	1,076	134
Expected return on plan assets	0	0	0
Settlement loss recognized	0	0	0
Amortization of net loss	(28)	0	0
Net periodic benefit cost (benefit)	$ 862	$ 1,157	$ 145