Earnings Per Common Share (Basic and Diluted Earnings per Common Share) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2013		Mar. 31, 2012		Mar. 31, 2011
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations																	$ 1,338		$ 1,403		$ 1,130
Discontinued operation – gain on sale, net of tax																	0		0		72
Net Income	$ 259	[1],[2],[3]	$ 298	[2],[4]	$ 401	[1],[2]	$ 380	[1],[5]	$ 521	[6],[7]	$ 300	[6],[7]	$ 296	[6]	$ 286		$ 1,338		$ 1,403		$ 1,202
Weighted average common shares outstanding:
Basic																	235		246		258
Effect of dilutive securities:
Diluted																	239		251		263
Diluted
Continuing operations																	$ 5.59	[8]	$ 5.59	[8]	$ 4.29	[8]
Discontinued operation – gain on sale																	$ 0.00	[8]	$ 0.00	[8]	$ 0.28	[8]
Total	$ 1.10	[1],[2],[3],[8]	$ 1.24	[2],[4],[8]	$ 1.67	[1],[2],[8]	$ 1.58	[1],[5],[8]	$ 2.09	[6],[7],[8]	$ 1.20	[6],[7],[8]	$ 1.18	[6],[8]	$ 1.13	[8]	$ 5.59	[8]	$ 5.59	[8]	$ 4.57	[8]
Basic
Continuing operations																	$ 5.71	[8]	$ 5.70	[8]	$ 4.37	[8]
Discontinued operation – gain on sale																	$ 0.00	[8]	$ 0.00	[8]	$ 0.28	[8]
Total	$ 1.12	[1],[2],[3],[8]	$ 1.27	[2],[4],[8]	$ 1.70	[1],[2],[8]	$ 1.61	[1],[5],[8]	$ 2.14	[6],[7],[8]	$ 1.22	[6],[7],[8]	$ 1.20	[6],[8]	$ 1.15	[8]	$ 5.71	[8]	$ 5.70	[8]	$ 4.65	[8]
Options [Member]
Effect of dilutive securities:
Dilutive securities																	1		2		3
Restricted Stock Units (RSUs) [Member]
Effect of dilutive securities:
Dilutive securities																	3		3		2

[1] Financial results for the first, second and fourth quarters of 2013 include AWP litigation charges of $16 million pre-tax ($10 million after-tax), $44 million pre-tax ($27 million after-tax) and $12 million pre-tax ($8 million after-tax), which were recorded in operating expenses.

[2] Financial results for the second, third and fourth quarters of 2013 include the pre-tax receipts of $19 million, $8 million and $17 million representing our share of settlements of antitrust class action lawsuits brought against drug manufacturers, which were recorded as a reduction to cost of sales.

[3] Financial results for the fourth quarter of 2013 include the following pre-tax impairment charges: an equity investment of $191 million, goodwill of $36 million, and capitalized software held for sale of $10 million.

[4] Financial results for the third quarter of 2013 include a $40 million pre-tax ($29 million after-tax) charge for a legal dispute in our Canadian business which was recorded in operating expenses.

[5] Financial results for the first quarter of 2013 include an $81 million pre-tax ($51 million after-tax) gain on business combination, which was recorded as a reduction to operating expenses.

[6] Financial results for the second, third and fourth quarters of 2012 include AWP litigation charges of $118 million pre-tax ($77 million after-tax), $27 million pre-tax ($15 million after-tax) and $4 million pre-tax (benefit of $32 million after-tax), which were recorded in operating expenses.

[7] Financial results for the third and fourth quarters of 2012 include product alignment pre-tax charges of $42 million and $9 million.

[8] Certain computations may reflect rounding adjustments.