Condensed Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 663,302	$ 570,721
Reverse Repurchase Agreements	2,968,000	0
Marketable securities	0	1,134,989
Accounts receivable, net	753,611	686,848
Due from unconsolidated joint business	267,429	268,395
Inventory	506,557	447,373
Other current assets	169,939	136,011
Total current assets	5,328,838	3,244,337
Marketable securities	0	2,036,658
Property, plant and equipment, net	1,736,811	1,742,226
Intangible assets, net	1,581,511	1,631,547
Goodwill	1,210,718	1,201,296
Investments and other assets	306,839	274,054
Total assets	10,164,717	10,130,118
Current liabilities:
Current portion of notes payable and line of credit	203,317	453,379
Taxes payable	28,045	20,066
Accounts payable	165,207	203,999
Accrued expenses and other	885,093	979,945
Total current liabilities	1,281,662	1,657,389
Notes payable and other financing arrangements	711,831	687,396
Long-term deferred tax liability	156,667	217,272
Other long-term liabilities	674,951	604,266
Total liabilities	2,825,111	3,166,323
Commitments and contingencies
Biogen Idec Inc. shareholders' equity
Preferred stock, par value $0.001 per share	0	0
Common stock, par value $0.0005 per share	128	127
Additional paid-in capital	3,858,955	3,854,525
Accumulated other comprehensive loss	(67,975)	(55,305)
Retained earnings	4,913,543	4,486,794
Treasury stock, at cost	(1,365,641)	(1,324,618)
Total Biogen Idec Inc. shareholders' equity	7,339,010	6,961,523
Noncontrolling interests	596	2,272
Total equity	7,339,606	6,963,795
Total liabilities and equity	$ 10,164,717	$ 10,130,118