Amounts Recognized (Pre-tax) in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Pension Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Future Amortization of Gain (Loss)	$ (10,100)
Net loss	117,640	$ 134,031
Prior service cost (credit)	8	30
Net amount recognized	117,648	134,061
Other Postretirement Employee Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Future Amortization of Gain (Loss)	(5,900)
Net loss	(20,906)	(29,290)
Prior service cost (credit)	(3,211)	(4,923)
Net amount recognized	$ (24,117)	$ (34,213)