Income Tax Expense Components of Deferred Tax (Assets) Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Income Tax Expense [Abstract]
Tax Credit Carryforward, Amount	$ (2,487)	$ (2,533)
Prepaid Income Taxes on CIAC	(66)	4
Deferred Tax Assets, Operating Loss Carryforwards	(385)	0
Deferred Tax - Other Comprehensive Income	(842)	(486)
Accelerated Depreciation	46,379	34,548
Unamortized Investment Tax Credits	1,490	1,313
Other Deferred Tax (Assets) Liabilities	(2,816)	(643)
Net Deferred Income Tax (Asset) Liability	$ 41,273	$ 32,203