Employee Benefits (Details 2) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2012	Mar. 31, 2011 Predecessor	Dec. 31, 2010 Predecessor
Health Care and Life Insurance
Health care benefit expenses	$ 167	$ 221	$ 57	$ 224