Condensed Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Cash receipts from customers	$ 28,018	$ 29,207
Cash paid for inventory and prescriptions dispensed by retail network pharmacies	(22,270)	(22,515)
Cash paid to other suppliers and employees	(3,889)	(3,751)
Interest received	1	1
Interest paid	(104)	(128)
Income taxes paid	(116)	(28)
Net cash provided by operating activities	1,640	2,786
Cash flows from investing activities:
Purchases of property and equipment	(318)	(376)
Proceeds from sale of property and equipment	5	0
Acquisitions (net of cash acquired) and other investments	(254)	(74)
Proceeds from sale of subsidiary	0	7
Net cash used in investing activities	(567)	(443)
Cash flows from financing activities:
Decrease in short-term debt	(390)	(750)
Repayments of long-term debt	0	(52)
Dividends paid	(277)	(211)
Proceeds from exercise of stock options	150	278
Excess tax benefits from stock-based compensation	13	0
Repurchase of common stock	(393)	(810)
Net cash used in financing activities	(897)	(1,545)
Net increase in cash and cash equivalents	176	798
Cash and cash equivalents at beginning of period	1,375	1,413
Cash and cash equivalents at end of period	1,551	2,211
Reconciliation of net income to net cash provided by operating activities:
Net income	956	775
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	502	423
Stock-based compensation	34	36
Deferred income taxes and other noncash items	66	21
Change in operating assets and liabilities, net of effects from acquisitions:
Accounts receivable, net	(113)	(70)
Inventories	193	(776)
Other current assets	238	286
Other assets	(135)	(189)
Accounts payable and claims and discounts payable	(230)	1,044
Accrued expenses	105	1,250
Other long-term liabilities	24	(14)
Net cash provided by operating activities	$ 1,640	$ 2,786