Pension and Other Post-Retirement Benefits (Other Changes Recognized in Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Current year actuarial (loss) gain	$ (21,517)	$ (48,505)	$ (90,106)
Amortization of actuarial loss	13,174	11,186	7,378
Amortization of prior service credit	0	0	0
Total recognized in comprehensive (loss) income	(8,343)	(37,319)	(82,728)
Other Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Current year actuarial (loss) gain	3	(159)	(293)
Amortization of actuarial loss	47	37	34
Amortization of prior service credit	(103)	(103)	(103)
Total recognized in comprehensive (loss) income	$ (53)	$ (225)	$ (362)