Pension and Other Post-Retirement Benefits (Pretax Amounts Included in Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Prior service credit	$ 0	$ 0
Net actuarial loss	330,887	322,451
Accumulated other comprehensive loss (income)	$ 330,887	$ 322,451
Other Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate	5.00%	5.00%	5.00%
Prior service credit	$ (1,196)	$ (1,299)
Net actuarial loss	770	820
Accumulated other comprehensive loss (income)	$ (426)	$ (479)