Income Taxes (Details 2) (USD $) In Millions, unless otherwise specified			12 Months Ended				12 Months Ended
	Dec. 31, 2012 Investment tax credits	Dec. 31, 2011 Investment tax credits	Dec. 31, 2012 QSC	Dec. 31, 2011 QSC	Dec. 31, 2010 Predecessor	Dec. 31, 2010 Predecessor Investment tax credits	Dec. 31, 2010 Predecessor QSC
Income taxes
Amount paid to QSC			$ 607	$ 211			$ 677
Income taxes reflected in advances to affiliates				19
Decrease in income tax expense as a result of the March 2010 enactments of the Patient Protection and Affordable Care Act and the Health Care and Education Reconciliation Act of 2010					251
State deferred tax expense (benefit ), net of federal effect resulting from changes in state tax rate					2
Unamortized investment tax credits	1	2				61
Amortization investment tax credits					$ 8