Goodwill and Intangible Assets - Intangible Assets Balances (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Cost	$ 326	$ 276
Accumulated Amortization	186	154
Carrying Amount	140	122
Contract rights and licenses
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Cost	267	224
Accumulated Amortization	148	120
Carrying Amount	119	104
Customer relationships
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Cost	25	25
Accumulated Amortization	24	23
Carrying Amount	1	2
Provider network
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Cost	34	27
Accumulated Amortization	14	11
Carrying Amount	$ 20	$ 16

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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