Supplemental Condensed Consolidating Financial Information and Other Collateral-Related Information - Schedule of Quarterly Consolidated Financial Information (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other Items Net Interest And Other Financial Income [Line Items]
Losses (gains) on sales of facilities	$ 6	$ 5	$ 1	$ 1	$ 84	$ 1	$ 1	$ 2	$ 15	$ 142	$ 4
Legal claim costs	110								175
Termination of management agreement								149		181
Losses on retirement of debt						256	47			481
Gain on purchase of facilities					$ 1,424					$ 1,522