Pension and Postretirement Benefits (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2015
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	$ 773,000	$ 734,000
Defined Benefit Plan, Interest Cost	1,262,000	1,542,000
Defined Benefit Plan, Expected Return on Plan Assets	(1,402,000)	(1,607,000)
Defined Benefit Plan, Amortization of Losses	881,000	789,000
Defined Benefit Plan, Amortization of Prior Service Cost	(26,000)	866,000
Defined Benefit Plan, Net Periodic Benefit Cost	1,488,000	2,324,000
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year			4,176,000
Defined Benefit Plan, Contributions by Employer	1,280,000
Effect of Plan Amendment on Net Periodic Benefit Cost		902,000
Prior Service Cost Charge per Diluted Share		$ 0.05
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	5,000	8,000
Defined Benefit Plan, Interest Cost	50,000	54,000
Defined Benefit Plan, Expected Return on Plan Assets	0	0
Defined Benefit Plan, Amortization of Losses	26,000	6,000
Defined Benefit Plan, Amortization of Prior Service Cost	0	0
Defined Benefit Plan, Net Periodic Benefit Cost	81,000	68,000
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year			568,000
Defined Benefit Plan, Contributions by Employer	$ 237,000