Details of Intangible Assets Included in Other Long-Term Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 9 months 18 days
Cost	$ 753	$ 865
Accumulated Amortization	396	425
Net	$ 357	440
Customer contracts/relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 9 months 18 days
Cost	$ 566	657
Accumulated Amortization	292	326
Net	$ 274	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	54	50
Net	$ 50	65
Provider contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	14 years 7 months 6 days
Cost	$ 51	52
Accumulated Amortization	24	21
Net	$ 27	31
Noncompetes and other
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years 2 months 12 days
Cost	$ 32	41
Accumulated Amortization	26	28
Net	$ 6	$ 13