Details of Intangible Assets Included in Other Long-Term Assets (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	10 years
Cost	$ 754	$ 865
Accumulated Amortization	335	425
Net	419	440
Customer contracts/ relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 10 months 24 days
Cost	565	657
Accumulated Amortization	248	326
Net	317	331
Trade names and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years 3 months 18 days
Cost	104	115
Accumulated Amortization	43	50
Net	61	65
Provider contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	15 years
Cost	51	52
Accumulated Amortization	22	21
Net	29	31
Noncompetes and other
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years
Cost	34	41
Accumulated Amortization	22	28
Net	$ 12	$ 13