Accumulated Other Comprehensive Income (Loss) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at December 31, 2012	$ (640)
Other comprehensive income (loss), before reclassifications	264
Reclassifications to Consolidated Statement of Income	91
Net other comprehensive income (loss)	355	(28)	(63)
Balance at December 31, 2013	(285)	(640)
Interest-rate Derivatives Previously Subject to Hedge Accounting [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at December 31, 2012	(61)
Other comprehensive income (loss), before reclassifications	0
Reclassifications to Consolidated Statement of Income	7
Net other comprehensive income (loss)	7
Balance at December 31, 2013	(54)
Pension and Other Postretirement Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at December 31, 2012	(579)
Other comprehensive income (loss), before reclassifications	264
Reclassifications to Consolidated Statement of Income	84
Net other comprehensive income (loss)	348
Balance at December 31, 2013	$ (231)