Quarterly Financial Information (Unaudited) - Narrative (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Quarterly Financial Information [Line Items]
Pretax charges related to last-in-first-out method of accounting for inventories									$ 244	$ 337	$ 311
Pre-tax charge	$ 229								229
Brazil Distribution Business
Quarterly Financial Information [Line Items]
Impairment charges, net of tax					$ 235
Controlled Substance Investigation
Quarterly Financial Information [Line Items]
Claims and litigation charges, after tax					150					$ 150
Cost of Sales
Quarterly Financial Information [Line Items]
Pre-tax charge	26
Operating Expenses
Quarterly Financial Information [Line Items]
Pre-tax charge	203
Operating Segments | Distribution Solutions
Quarterly Financial Information [Line Items]
Pretax charges related to last-in-first-out method of accounting for inventories	29	$ 33	$ 91	$ 91	$ 50	$ 95	$ 94	$ 98
Net cash proceeds		$ 17		59					76
Pre-tax charge	161								161
Operating Segments | Distribution Solutions | ZEE Medical Business
Quarterly Financial Information [Line Items]
Gain from sale of business, after tax			$ 29
Operating Segments | Distribution Solutions | Cost of Sales
Quarterly Financial Information [Line Items]
Pre-tax charge	5
Operating Segments | Distribution Solutions | Operating Expenses
Quarterly Financial Information [Line Items]
Pre-tax charge	156
Operating Segments | Technology Solutions
Quarterly Financial Information [Line Items]
Pre-tax charge	51								$ 51
Operating Segments | Technology Solutions | Nurse Triage
Quarterly Financial Information [Line Items]
Gain from sale of business, after tax				$ 38
Operating Segments | Technology Solutions | Cost of Sales
Quarterly Financial Information [Line Items]
Pre-tax charge	21
Operating Segments | Technology Solutions | Operating Expenses
Quarterly Financial Information [Line Items]
Pre-tax charge	$ 30