Pension and Other Postretirement Plans (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Deferred pension and OPRB costs recovered [Abstract]
Deferred pension and OPRB costs recovered	$ 300,000	$ 300,000
Pension Benefits [Member]
Components of net periodic benefit cost [Line Items]
Service cost	1,929,000	1,823,000
Interest cost	3,186,000	3,154,000
Expected return on assets	(4,776,000)	(3,818,000)
Amortization of:
Prior service cost	79,000	108,000
Actuarial loss	2,015,000	2,006,000
Net periodic benefit cost	2,433,000	3,273,000
Postretirement Benefits [Member]
Components of net periodic benefit cost [Line Items]
Service cost	596,000	647,000
Interest cost	970,000	1,125,000
Expected return on assets	(544,000)	(435,000)
Amortization of:
Transition obligation	1,000	106,000
Prior service cost	28,000	28,000
Actuarial loss	311,000	621,000
Net periodic benefit cost	$ 1,362,000	$ 2,092,000