Details of Intangible Assets Included in Other Long-Term Assets (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 10 months 24 days
Cost	$ 757	$ 865
Accumulated Amortization	356	425
Net	$ 401	440
Customer contracts/ relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 10 months 24 days
Cost	$ 567	657
Accumulated Amortization	263	326
Net	$ 304	331
Trade names and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years 2 months 12 days
Cost	$ 105	115
Accumulated Amortization	47	50
Net	$ 58	65
Provider contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	14 years 10 months 24 days
Cost	$ 52	52
Accumulated Amortization	23	21
Net	$ 29	31
Noncompetes and other
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years
Cost	$ 33	41
Accumulated Amortization	23	28
Net	$ 10	$ 13