Nonpension Postretirement Benefits (Amounts Recognized in Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Current liability	$ 4,892	$ 4,903
Long-term liability	55,373	55,282
Nonpension Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Current liability	4,892	4,903
Long-term liability	55,373	55,282
Total accrued postretirement benefit liability	$ 60,265	$ 60,185