Changes in Carrying Amount of Goodwill by Reportable Segments (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Goodwill [Roll Forward]
Beginning balance	$ 3,231	$ 3,253
Acquisitions	35	19
Dispositions	(1)	(40)
Subsequent payments/adjustments		(1)
Ending balance	3,265	3,231
Retail
Goodwill [Roll Forward]
Beginning balance	1,069	1,069
Acquisitions	0	0
Dispositions	0	0
Subsequent payments/adjustments		0
Ending balance	1,069	1,069
Group
Goodwill [Roll Forward]
Beginning balance	385	385
Acquisitions	0	0
Dispositions	0	0
Subsequent payments/adjustments		0
Ending balance	385	385
Healthcare Services
Goodwill [Roll Forward]
Beginning balance	1,777	1,799
Acquisitions	35	19
Dispositions	(1)	(40)
Subsequent payments/adjustments		(1)
Ending balance	$ 1,811	$ 1,777

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

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- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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- Definition

Amount of increase (decrease) of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of divestiture of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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