Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities:
Net income	$ 1,202,860	$ 917,419
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	355,102	225,880
Share-based compensation	83,856	67,387
Deferred income taxes	(146,506)	(118,047)
Other	(64,213)	(42,495)
Changes in operating assets and liabilities, net:
Accounts receivable	(188,961)	(185,688)
Inventory	(72,689)	(129,171)
Accrued expenses and other current liabilities	(30,299)	(15,970)
Other changes in operating assets and liabilities, net	(43,931)	84,836
Net cash flows provided by operating activities	1,095,219	804,151
Cash flows from investing activities:
Proceeds from sales and maturities of marketable securities	1,317,525	4,404,707
Purchases of marketable securities	(1,787,606)	(1,617,974)
Acquisition of TYSABRI rights	0	(3,262,719)
Purchases of property, plant and equipment	(118,308)	(87,440)
Acquisitions of business, net of cash acquired	(25,000)	0
Other	(10,745)	(6,874)
Net cash flows used in investing activities	(624,134)	(570,300)
Cash flows from financing activities:
Purchase of treasury stock	(336,905)	(41,023)
Proceeds from issuance of stock for share-based compensation arrangements	33,477	39,002
Repayment of borrowings under senior notes	0	(452,340)
Excess tax benefit from stock options	83,940	53,311
Other	12,003	(8,137)
Net cash flows used in financing activities	(207,485)	(409,187)
Net increase (decrease) in cash and cash equivalents	263,600	(175,336)
Effect of exchange rate changes on cash and cash equivalents	(2,965)	(2,878)
Cash and cash equivalents, beginning of the period	602,562	570,721
Cash and cash equivalents, end of the period	$ 863,197	$ 392,507