Details of Intangible Assets Included in Other Long-Term Assets (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	10 years 4 months 24 days
Cost	$ 1,025	$ 648
Accumulated Amortization	294	213
Net	731	435
Customer contracts/relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 6 months
Cost	733	429
Accumulated Amortization	237	182
Net	496	247
Trade names and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	13 years 7 months 6 days
Cost	190	135
Accumulated Amortization	21	6
Net	169	129
Provider contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	15 years
Cost	51	44
Accumulated Amortization	19	15
Net	32	29
Noncompetes And Other
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	6 years 6 months
Cost	51	40
Accumulated Amortization	17	10
Net	$ 34	$ 30