Condensed Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 427,811	$ 570,721
Marketable securities	240,882	1,134,989
Accounts receivable, net	891,396	686,848
Due from unconsolidated joint business, net	263,465	268,395
Inventory	614,483	447,373
Other current assets	205,635	136,011
Total current assets	2,643,672	3,244,337
Marketable securities	373,558	2,036,658
Property, plant and equipment, net	1,806,074	1,742,226
Intangible assets, net	4,580,199	1,631,547
Goodwill	1,210,718	1,201,296
Investments and other assets	636,028	274,054
Total assets	11,250,249	10,130,118
Current liabilities:
Current portion of notes payable and line of credit	3,385	453,379
Taxes payable	144,180	20,066
Accounts payable	166,709	203,999
Accrued expenses and other	1,204,437	979,945
Total current liabilities	1,518,711	1,657,389
Notes payable and other financing arrangements	694,894	687,396
Long-term deferred tax liability	302,483	217,272
Other long-term liabilities	608,473	604,266
Total liabilities	3,124,561	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	3,987,377	3,854,525
Accumulated other comprehensive loss	(29,315)	(55,305)
Retained earnings	5,891,829	4,486,794
Treasury stock, at cost	(1,724,927)	(1,324,618)
Total Biogen Idec Inc. shareholders' equity	8,125,092	6,961,523
Noncontrolling interests	596	2,272
Total equity	8,125,688	6,963,795
Total liabilities and equity	$ 11,250,249	$ 10,130,118