CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Millions, unless otherwise specified	9 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2012 Successor	Mar. 25, 2012 Predecessor	Dec. 31, 2011 Predecessor	Dec. 31, 2010 Predecessor
Statement of Income and Comprehensive Income [Line Items]
Net income	$ 88	$ 40	$ 168	$ 148
Other comprehensive income (loss), net of tax:
Reclassification of unrealized loss on interest rate hedges into earnings	0	3	13	13
Change in fair value of interest rate hedges	0	0	(1)	(8)
Actuarial loss relating to postretirement benefits	(9)	0	(10)	(1)
Reclassification of prior service credit relating to other postretirement benefits into earnings	0	0	(1)	(1)
Total other comprehensive income, net of tax	(9)	3	1	3
Comprehensive income	$ 79	$ 43	$ 169	$ 151