Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Pension and Supplemental Executive Retirement Plans [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost	$ 2,142	$ 2,835	$ 6,425	$ 8,504
Interest Cost	3,997	3,823	11,991	11,467
Expected return on plan assets	(5,258)	(5,035)	(15,773)	(15,108)
Recognized net actuarial loss	271	1,536	812	4,609
Amortization of prior service cost	(233)	125	(698)	377
Net periodic benefit cost	919	3,284	2,757	9,849
Other Postretirement Benefits [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost	165	202	494	609
Interest Cost	164	155	491	464
Expected return on plan assets	(1,162)	(919)	(3,486)	(2,759)
Recognized net actuarial loss	(109)	0	(326)	0
Amortization of prior service cost	(1,663)	(1,663)	(4,988)	(4,987)
Net periodic benefit cost	$ (2,605)	$ (2,225)	$ (7,815)	$ (6,673)