Basis of Presentation and Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								9 Months Ended	12 Months Ended		3 Months Ended	12 Months Ended
	Dec. 31, 2013 state	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 state	Dec. 31, 2012	Mar. 31, 2011 Predecessor	Dec. 31, 2013 Error Correction	Dec. 31, 2013 Deferred Tax Asset Error Correction	Dec. 31, 2013 Other Noncurrent Liabilities Error Correction
Basis of presentation
Number of states in which service is provided (states)	14									14
Increase (decrease) in deferred income taxes														$ 17	$ 2
Goodwill													(15)
Net Income (Loss) Attributable to Parent	236	218	246	264	241	212	178	218	543	964	849	299
Tax benefit associated with deduction for pension funding recognized in equity contribution								$ 100			$ 100