Pension and Other Post-Retirement Benefits Pension Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Service Cost	$ 486	$ 318	$ 1,010	$ 761
Defined Benefit Plan, Interest Cost	640	522	1,285	1,067
Defined Benefit Plan, Expected Return on Plan Assets	(659)	(553)	(1,346)	(1,228)
Defined Benefit Plan, Amortization of Transition Obligations (Assets)	0	1	0	1
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	20	17	37	34
Defined Benefit Plan, Amortization of Gains (Losses)	519	156	877	344
Defined Benefit Plan, Net Periodic Benefit Cost	1,006	461	1,863	979
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Service Cost	118	159	275	346
Defined Benefit Plan, Interest Cost	129	154	270	333
Defined Benefit Plan, Expected Return on Plan Assets	(67)	(59)	(135)	(134)
Defined benefit plan amortization of regulatory assets	56	56	112	112
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(202)	(163)	(403)	(264)
Defined Benefit Plan, Amortization of Gains (Losses)	140	144	306	304
Defined Benefit Plan, Net Periodic Benefit Cost	$ 174	$ 291	$ 425	$ 697