Consolidation and Nature of Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Cash Flows from Operating Activities
Deferred income taxes	$ 8,810	$ (9,265)
Deferred investment tax credit	(247)	21,428
Income tax receivable	130,870	(433)
Accrued taxes	48,139	39,615
Cash paid (received) during the period for:
Income taxes, net of refunds	(131,078)	425
Interest, net of amounts capitalized	49,147	49,038
Significant non-cash investing and financing activities:
Accrued capital expenditures	24,908	6,575
As previously reported
Cash Flows from Operating Activities
Deferred income taxes		12,163
Accrued taxes and income tax receivable		39,182
Changes to conform to current year presentation
Cash Flows from Operating Activities
Deferred income taxes		(21,428)
Deferred investment tax credit		21,428
Accrued taxes and income tax receivable		(39,182)
Income tax receivable		(433)
Accrued taxes		$ 39,615