Changes In Carrying Amount Of Goodwill By Reportable Segments (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
Goodwill [Line Items]
Balance at January 1, 2012	$ 2,740
Acquisitions	52
Balance at June 30, 2012	2,792
Retail
Goodwill [Line Items]
Balance at January 1, 2012	754
Acquisitions	43
Balance at June 30, 2012	797
Employer Group
Goodwill [Line Items]
Balance at January 1, 2012	62
Acquisitions	0
Balance at June 30, 2012	62
Health And Well-Being Services
Goodwill [Line Items]
Balance at January 1, 2012	1,867
Acquisitions	9
Balance at June 30, 2012	1,876
Other Businesses
Goodwill [Line Items]
Balance at January 1, 2012	57
Acquisitions	0
Balance at June 30, 2012	$ 57