Goodwill and Intangible Assets-Intangible Assets by Type (Detail) (USD $) In Millions, unless otherwise specified							3 Months Ended			3 Months Ended			3 Months Ended			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2013 Finite-lived Intangible Assets	Dec. 31, 2012 Finite-lived Intangible Assets	Mar. 31, 2013 Finite-lived Intangible Assets Weighted Average [Member]	Mar. 31, 2013 Finite-lived Intangible Assets Customer Relationships	Dec. 31, 2012 Finite-lived Intangible Assets Customer Relationships	Mar. 31, 2013 Finite-lived Intangible Assets Customer Relationships Weighted Average [Member]	Mar. 31, 2013 Finite-lived Intangible Assets Customer Contracts	Dec. 31, 2012 Finite-lived Intangible Assets Customer Contracts	Mar. 31, 2013 Finite-lived Intangible Assets Customer Contracts Weighted Average [Member]	Mar. 31, 2013 Finite-lived Intangible Assets Other Intangible Assets	Dec. 31, 2012 Finite-lived Intangible Assets Other Intangible Assets	Mar. 31, 2013 Finite-lived Intangible Assets Other Intangible Assets Weighted Average [Member]	Mar. 31, 2013 Indefinite-lived Intangible Assets	Dec. 31, 2012 Indefinite-lived Intangible Assets	Mar. 31, 2013 Indefinite-lived Intangible Assets Customer Relationships		Dec. 31, 2012 Indefinite-lived Intangible Assets Customer Relationships		Mar. 31, 2013 Indefinite-lived Intangible Assets Trade Name		Dec. 31, 2012 Indefinite-lived Intangible Assets Trade Name
Intangible Assets by Major Class [Line Items]
Gross carrying amount	$ 7,209				$ 4,533			$ 2,062			$ 2,348			$ 123			$ 2,676		$ 1,310	[1]			$ 1,366	[1]
Accumulated amortization	(2,513)				(2,513)			(1,351)			(1,061)			(101)
Net carrying amount	$ 4,696	$ 4,809	$ 5,072	$ 5,152	$ 2,020	$ 2,121		$ 711	$ 761		$ 1,287	$ 1,335		$ 22	$ 25		$ 2,676	$ 2,688	$ 1,310	[1]	$ 1,320	[1]	$ 1,366	[1]	$ 1,368	[1]
Remaining weighted average amortization period							12 years			12 years			12 years			5 years

[1] Intangible assets not subject to amortization have an indefinite life.