Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension and Supplemental Executive Retirement Plans [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost	$ 2,080	$ 2,717
Interest Cost	4,009	3,799
Expected Return on Assets	(5,258)	(5,038)
Recognized net actuarial loss	291	1,516
Amortization of prior service cost	(42)	125
Net periodic benefit cost	1,080	3,119
Other Postretirement Benefits [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost	177	194
Interest Cost	183	154
Expected Return on Assets	(1,161)	(920)
Recognized net actuarial loss	(73)	0
Amortization of prior service cost	(1,662)	(1,663)
Net periodic benefit cost	$ (2,536)	$ (2,235)