Debt Debt Capital Leases (Details) (USD $) In Millions, unless otherwise specified	11 Months Ended	12 Months Ended		1 Months Ended	11 Months Ended
	Dec. 31, 2010 Successor [Member] Capital Lease Obligations [Member]	Dec. 31, 2012 Successor [Member] Capital Lease Obligations [Member]	Dec. 31, 2011 Successor [Member] Capital Lease Obligations [Member]	Feb. 12, 2010 Predecessor [Member] Capital Lease Obligations [Member]	Dec. 31, 2010 Minimum [Member]	Dec. 31, 2010 Maximum [Member]
Debt Instrument [Line Items]
Capital leases entered into to finance maintenance of way and other vehicles and equipment	$ 40	$ 0	$ 0	$ 8
Lease Term					5 years	7 years