Consolidated Statements of Income (USD $) In Millions, unless otherwise specified	11 Months Ended	12 Months Ended		1 Months Ended
	Dec. 31, 2010 Successor [Member]	Dec. 31, 2012 Successor [Member]	Dec. 31, 2011 Successor [Member]	Feb. 12, 2010 Predecessor [Member]
Revenues	$ 15,059	$ 20,835	$ 19,548	$ 1,791
Operating expenses:
Compensation and benefits	3,562	4,505	4,315	442
Fuel	2,687	4,459	4,267	329
Purchased services	1,890	2,374	2,218	279
Depreciation and amortization	1,532	1,889	1,807	192
Equipment rents	670	810	779	97
Materials and other	665	786	852	1
Total operating expenses	11,006	14,823	14,238	1,340
Operating income	4,053	6,012	5,310	451
Interest expense	435	623	560	72
Other expense, net	7	12	9	2
Income before income taxes	3,611	5,377	4,741	377
Income tax expense	1,376	2,005	1,769	153
Net income	$ 2,235	$ 3,372	$ 2,972	$ 224