Consolidation and Nature of Operations (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Cash Flows from Operating Activities
Deferred income taxes	$ 68,526	$ 61,109
Deferred investment tax credit	119,979	5,033	99,819
Deferred credits - other	191,259		183,835
Cash paid during the period for:
Income taxes, net of (refunds)	(9)	(649)
Interest, net of amounts capitalized	91,346	94,680
Significant non-cash investing and financing activities:
Accrued capital expenditures	8,904	14,745
Dividends accrued but not paid	59,946	57,479
As previously reported
Cash Flows from Operating Activities
Deferred income taxes		66,142
Deferred credits - other			283,654
Reclassifications
Cash Flows from Operating Activities
Deferred income taxes		(5,033)
Deferred investment tax credit		5,033	99,819
Deferred credits - other			$ (99,819)