Changes in Carrying Amount of Goodwill by Reportable Segments (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2015 USD ($)
Goodwill [Roll Forward]
Balance at January 1, 2015	$ 3,231
Acquisitions	35
Balance at June 30, 2015	3,266
Retail
Goodwill [Roll Forward]
Balance at January 1, 2015	1,069
Acquisitions	0
Balance at June 30, 2015	1,069
Group
Goodwill [Roll Forward]
Balance at January 1, 2015	385
Acquisitions	0
Balance at June 30, 2015	385
Healthcare Services
Goodwill [Roll Forward]
Balance at January 1, 2015	1,777
Acquisitions	35
Balance at June 30, 2015	1,812
Other Businesses
Goodwill [Roll Forward]
Balance at January 1, 2015	0
Acquisitions	0
Balance at June 30, 2015	$ 0