Details of Intangible Assets Included in Other Long-Term Assets (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	10 years 3 months 18 days
Cost	$ 1,093	$ 1,025
Accumulated Amortization	369	294
Net	724	731
Customer contracts/relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 7 months 6 days
Cost	792	733
Accumulated Amortization	287	237
Net	505	496
Trade names and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	13 years 1 month 6 days
Cost	198	190
Accumulated Amortization	34	21
Net	164	169
Provider contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	15 years
Cost	51	51
Accumulated Amortization	22	19
Net	29	32
Noncompetes And Other
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	6 years 6 months
Cost	52	51
Accumulated Amortization	26	17
Net	$ 26	$ 34