Pension and Postretirement Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2014
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	$ 734	$ 838
Defined Benefit Plan, Interest Cost	1,542	1,380
Defined Benefit Plan, Expected Return on Plan Assets	(1,607)	(1,478)
Defined Benefit Plan, Amortization of Losses	789	981
Defined Benefit Plan, Amortization of Prior Service Cost	866	28
Defined Benefit Plan, Net Periodic Benefit Cost	2,324	1,749
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year			6,172
Defined Benefit Plan, Contributions by Employer	3,854
Effect of Plan Amendment on Net Periodic Benefit Cost	902
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	8	13
Defined Benefit Plan, Interest Cost	54	56
Defined Benefit Plan, Expected Return on Plan Assets	0	0
Defined Benefit Plan, Amortization of Losses	6	47
Defined Benefit Plan, Amortization of Prior Service Cost	0	0
Defined Benefit Plan, Net Periodic Benefit Cost	68	116
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year			607
Defined Benefit Plan, Contributions by Employer	$ 211