Changes in Carrying Amount of Goodwill by Reportable Segments (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Goodwill [Line Items]
Goodwill reclassified as held-for-sale	$ 480
Balance at March 31, 2015	3,231	3,231
Retail
Goodwill [Line Items]
Balance at March 31, 2015	1,069
Group
Goodwill [Line Items]
Balance at March 31, 2015	385
Healthcare Services
Goodwill [Line Items]
Balance at March 31, 2015	1,777
Other Businesses
Goodwill [Line Items]
Balance at March 31, 2015	$ 0