Significant Accounting Policies (Narrative) (Details) (USD $)	3 Months Ended								12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2012 Y		Mar. 31, 2011		Mar. 31, 2010
Significant Accounting Policies [Line Items]
Percentage of LIFO inventory	88.00%				87.00%				88.00%		87.00%
LIFO reserves, net of LCM adjustments	$ 107,000,000				$ 96,000,000				$ 107,000,000		$ 96,000,000
Net LIFO expense									11,000,000		3,000,000		8,000,000
Excess of LIFO inventory over FIFO inventory	76,000,000				156,000,000				76,000,000		156,000,000
LCM charges recorded									(80,000,000)		44,000,000
Property plant and equipment minimum life, years									1
Property plant and equipment maximum life, years									30
Useful lives of capitalized software held for sale, years									3
Intangible assets useful life minimum									1
Intangible assets useful life maximum									20
Capitalized software	445,000,000				446,000,000				445,000,000		446,000,000
Accumulated amortization	902,000,000				778,000,000				902,000,000		778,000,000
Capitalized software held for sale	144,000,000				152,000,000				144,000,000		152,000,000
Sales return from customers									1,600,000,000		1,400,000,000		1,200,000,000
Segment reporting revenue by country	31,699,000,000	30,839,000,000	30,216,000,000	29,980,000,000	28,853,000,000	28,247,000,000	27,534,000,000	27,450,000,000	122,734,000,000		112,084,000,000		108,702,000,000
Deferred revenue	1,423,000,000				1,321,000,000				1,423,000,000		1,321,000,000
Supplier reserves	115,000,000				102,000,000				115,000,000		102,000,000
Sales Revenue, Segment [Member]
Significant Accounting Policies [Line Items]
Percentage of revenue and accounts receivable by large customers	52.00%								52.00%
Accounts Receivable [Member]
Significant Accounting Policies [Line Items]
Percentage of revenue and accounts receivable by large customers	49.00%								49.00%
CVS Caremark Corporation [Member] | Sales Revenue, Segment [Member]
Significant Accounting Policies [Line Items]
Percentage of revenue and accounts receivable by large customers	16.00%								16.00%
CVS Caremark Corporation [Member] | Accounts Receivable [Member]
Significant Accounting Policies [Line Items]
Percentage of revenue and accounts receivable by large customers	17.00%								17.00%
Wal-Mart Stores, Inc [Member] | Accounts Receivable [Member]
Significant Accounting Policies [Line Items]
Percentage of revenue and accounts receivable by large customers	10.00%								10.00%
Rite Aid Corporation [Member] | Sales Revenue, Segment [Member]
Significant Accounting Policies [Line Items]
Percentage of revenue and accounts receivable by large customers	10.00%								10.00%
Rite Aid Corporation [Member] | Accounts Receivable [Member]
Significant Accounting Policies [Line Items]
Percentage of revenue and accounts receivable by large customers	9.00%								9.00%
Capitalized Software Held For Internal Use [Member]
Significant Accounting Policies [Line Items]
Intangible assets useful life minimum									1
Intangible assets useful life maximum									10
Technology Solutions [Member]
Significant Accounting Policies [Line Items]
Segment reporting revenue by country									3,310,000,000		3,195,000,000		3,124,000,000
Deferred revenue	3,000,000				25,000,000				3,000,000		25,000,000
Distribution Solutions - Sales To Customers' Warehouses [Member]
Significant Accounting Policies [Line Items]
Segment reporting revenue by country									20,453,000,000	[1]	18,631,000,000	[1]	21,435,000,000	[1]
Accounts Receivable Sales Facility [Member]
Significant Accounting Policies [Line Items]
Accounts receivable sales facility	$ 1,350,000,000								$ 1,350,000,000

[1] Revenues derived from services represent less than 2% of this segment's total revenues for 2012, 2011 and 2010.