Pension and Postretirement Benefits (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Mar. 31, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	$ 763	$ 716		$ 2,297	$ 2,186
Defined Benefit Plan, Interest Cost	1,256	1,506		3,772	4,567
Defined Benefit Plan, Expected Return on Plan Assets	(1,367)	(1,588)		(4,165)	(4,796)
Defined Benefit Plan, Amortization of Losses	862	763		2,620	2,311
Defined Benefit Plan, Amortization of Prior Service Cost	(25)	(21)		(76)	830
Defined Benefit Plan, Net Periodic Benefit Cost	1,489	1,376		4,448	5,098
Defined Benefit Plan, Contributions by Employer				1,835
Effect of Plan Amendment on Net Periodic Benefit Cost			$ 902
Prior Service Cost Charge per Diluted Share			$ 0.05
Pension Plans, Defined Benefit [Member] | 2015 Year [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year				4,176
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	1	5		12	15
Defined Benefit Plan, Interest Cost	47	58		146	174
Defined Benefit Plan, Expected Return on Plan Assets	0	0		0	0
Defined Benefit Plan, Amortization of Losses	12	16		64	48
Defined Benefit Plan, Amortization of Prior Service Cost	0	0		0	0
Defined Benefit Plan, Net Periodic Benefit Cost	$ 60	$ 79		222	$ 237
Defined Benefit Plan, Contributions by Employer				449
Other Postretirement Benefit Plans, Defined Benefit [Member] | 2015 Year [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year				$ 568