Consolidation and Nature of Operations (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Cash Flows from Operating Activities
Deferred income taxes	$ 256,132	$ 197,527
Deferred investment tax credit	115,984	8,974	99,819
Deferred credits - other	178,053		183,835
Income tax receivable	(131,128)	6,466
Accrued taxes	58,919	69,899
Change in long-term income tax receivable	137,270	(1,320)
Change in other long-term assets	(24,345)	(13,885)
Cash paid during the period for:
Income taxes, net of (refunds)	3,412	(651)
Interest, net of amounts capitalized	141,047	152,582
Significant non-cash investing and financing activities:
Accrued capital expenditures	11,377	11,281
As previously reported
Cash Flows from Operating Activities
Deferred income taxes		206,501
Deferred credits - other			283,654
Accrued taxes		76,365
Change in other long-term assets		(15,205)
Reclassifications
Cash Flows from Operating Activities
Deferred income taxes		(8,974)
Deferred investment tax credit		8,974	99,819
Deferred credits - other			(99,819)
Income tax receivable		6,466
Accrued taxes		(6,466)
Change in long-term income tax receivable		(1,320)
Change in other long-term assets		$ 1,320