Goodwill And Intangible Assets, Net (Information Regarding Intangible Assets) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2014	Mar. 31, 2014
Intangible assets
Gross Carrying Amount	$ 5,855	$ 6,353
Accumulated Amortization	(1,465)	(1,331)
Net Carrying Amount	4,390	5,022
Customer lists
Intangible assets
Weighted Average Remaining Amortization Period (years)	9 years
Gross Carrying Amount	3,022	3,384
Accumulated Amortization	(937)	(863)
Net Carrying Amount	2,085	2,521
Service agreements
Intangible assets
Weighted Average Remaining Amortization Period (years)	16 years
Gross Carrying Amount	1,014	995
Accumulated Amortization	(189)	(173)
Net Carrying Amount	825	822
Pharmacy Licenses
Intangible assets
Weighted Average Remaining Amortization Period (years)	27 years
Gross Carrying Amount	1,051	1,219
Accumulated Amortization	(28)	(11)
Net Carrying Amount	1,023	1,208
Trademarks and trade names
Intangible assets
Weighted Average Remaining Amortization Period (years)	15 years
Gross Carrying Amount	377	371
Accumulated Amortization	(68)	(59)
Net Carrying Amount	309	312
Technology-Based Intangible Assets
Intangible assets
Weighted Average Remaining Amortization Period (years)	3 years
Gross Carrying Amount	218	219
Accumulated Amortization	(177)	(173)
Net Carrying Amount	41	46
Other
Intangible assets
Weighted Average Remaining Amortization Period (years)	4 years
Gross Carrying Amount	173	165
Accumulated Amortization	(66)	(52)
Net Carrying Amount	$ 107	$ 113