Pension and Other Post-Retirement Benefits (Other Changes Recognized in Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Current year actuarial (loss) gain	$ (90,106)	$ 54,111	$ (51,882)
Amortization of actuarial loss	7,378	10,627	8,585
Current year prior service credit	0	0	0
Amortization of prior service cost (credit)	0	32	44
Total recognized in comprehensive (loss) income	(82,728)	64,770	(43,253)
Other Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Current year actuarial (loss) gain	(293)	1,403	(150)
Amortization of actuarial loss	34	8	86
Current year prior service credit	0	1,506	0
Amortization of prior service cost (credit)	(103)	0	0
Total recognized in comprehensive (loss) income	$ (362)	$ 2,917	$ (64)