Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net income	$ 1,405,035	$ 1,087,906
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	373,357	268,772
Share-based compensation	104,851	88,378
Deferred income taxes	(166,187)	(86,858)
Other	(36,577)	6,043
Changes in operating assets and liabilities, net:
Accounts receivable	(219,860)	18,486
Inventory	(182,814)	(82,423)
Other changes in operating assets and liabilities, net	198,268	71,686
Net cash flows provided by operating activities	1,476,073	1,371,990
Cash flows from investing activities:
Proceeds from sales and maturities of marketable securities	5,025,218	1,913,381
Purchases of marketable securities	(2,473,609)	(2,192,343)
Acquisition of TYSABRI rights	(3,262,719)	0
Acquisitions of business, net of cash acquired	0	(72,401)
Purchases of property, plant and equipment	(167,628)	(185,511)
Other	(15,954)	(38,014)
Net cash flows used in investing activities	(894,692)	(574,888)
Cash flows from financing activities:
Purchase of treasury stock	(400,308)	(963,171)
Proceeds from issuance of stock for share-based compensation arrangements	56,367	58,278
Repayments of borrowings under senior notes	(452,340)	0
Other	68,572	42,939
Net cash flows used in financing activities	(727,709)	(861,954)
Net decrease in cash and cash equivalents	(146,328)	(64,852)
Effect of exchange rate changes on cash and cash equivalents	3,418	2,033
Cash and cash equivalents, beginning of the period	570,721	514,542
Cash and cash equivalents, end of the period	$ 427,811	$ 451,723