Consolidated Statement of Cash Flows (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Consolidated Statement of Cash Flows [Abstract]
Increase to property, plant and equipment	$ (386,462)	$ (352,674)	$ (328,190)
Changes in related accounts payable and accrued liabilities	791	(23,828)	24,732
Property, plant and equipment additions, net of equity AFUDC*	(385,671)	(376,502)	(303,458)
Supplemental disclosures of cash flow information:
Interest (exclusive of amount capitalized)	88,357	89,342	89,150
Income taxes paid	728	31	21,457
Income tax refunds received	0	0	(455)
Supplemental disclosures of significant non-cash transactions:
Loans to parent reclassified to equity	$ 0	$ 0	$ (195,320)