Aggregate Debt Maturities (Detail) (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended			1 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jan. 31, 2014 Subsequent Event	Dec. 31, 2013 Subsequent Event Credit facility	Dec. 31, 2013 Subsequent Event Series Q Senior Notes Due February 2014
Debt Instrument [Line Items]
Repayment of credit facility revolver	$ 207	$ 89	$ 90	$ 225	$ 225
Repayment of Senior notes	$ 801	$ 1,795	$ 404			$ 150