Condensed Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Cash flows from operating activities:
Cash receipts from customers	$ 29,207	$ 22,971
Cash paid for inventory and prescriptions dispensed by retail network pharmacies	(22,515)	(17,445)
Cash paid to other suppliers and employees	(3,751)	(3,342)
Interest received	1	1
Interest paid	(128)	(150)
Income taxes paid	(28)	(169)
Net cash provided by operating activities	2,786	1,866
Cash flows from investing activities:
Purchases of property and equipment	(376)	(309)
Proceeds from sale-leaseback transactions		11
Proceeds from sale of property and equipment		12
Acquisitions (net of cash acquired) and other investments	(74)	(11)
Purchase of available-for-sale investments		(2)
Proceeds from sale of subsidiary	7
Net cash used in investing activities	(443)	(299)
Cash flows from financing activities:
Decrease in short-term debt	(750)
Repayments of long-term debt	(52)	(301)
Dividends paid	(211)	(171)
Proceeds from exercise of stock options	278	107
Repurchase of common stock	(810)	(467)
Net cash used in financing activities	(1,545)	(832)
Net increase in cash and cash equivalents	798	735
Cash and cash equivalents at beginning of period	1,413	1,427
Cash and cash equivalents at end of period	2,211	2,162
Reconciliation of net income to net cash provided by operating activities:
Net income	775	712
Adjustments required to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	423	374
Stock-based compensation	36	36
Deferred income taxes and other noncash items	21	70
Change in operating assets and liabilities, net of effects from acquisitions:
Accounts receivable, net	(70)	(423)
Inventories	(776)	514
Other current assets	286	(30)
Other assets	(189)	(52)
Accounts payable	1,044	535
Accrued expenses	1,250	156
Other long-term liabilities	(14)	(26)
Net cash provided by operating activities	$ 2,786	$ 1,866