Condensed Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 392,507	$ 570,721
Marketable securities	275,163	1,134,989
Accounts receivable, net	861,457	686,848
Due from unconsolidated joint business	249,996	268,395
Inventory	570,390	447,373
Other current assets	173,708	136,011
Total current assets	2,523,221	3,244,337
Marketable securities	107,139	2,036,658
Property, plant and equipment, net	1,787,776	1,742,226
Intangible assets, net	4,678,884	1,631,547
Goodwill	1,210,718	1,201,296
Investments and other assets	533,852	274,054
Total assets	10,841,590	10,130,118
Current liabilities:
Current portion of notes payable and line of credit	3,188	453,379
Taxes payable	81,563	20,066
Accounts payable	163,094	203,999
Accrued expenses and other	1,056,229	979,945
Total current liabilities	1,304,074	1,657,389
Notes payable and other financing arrangements	726,388	687,396
Long-term deferred tax liability	313,341	217,272
Other long-term liabilities	595,642	604,266
Total liabilities	2,939,445	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	3,917,985	3,854,525
Accumulated other comprehensive loss	(55,136)	(55,305)
Retained earnings	5,404,213	4,486,794
Treasury stock, at cost	(1,365,641)	(1,324,618)
Total Biogen Idec Inc. shareholders' equity	7,901,549	6,961,523
Noncontrolling interests	596	2,272
Total equity	7,902,145	6,963,795
Total liabilities and equity	$ 10,841,590	$ 10,130,118