Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 514,542	$ 759,598
Marketable securities	1,176,115	448,146
Accounts receivable, net of allowances of $57,524 and $54,922, respectively	584,603	605,329
Due from unconsolidated joint business	228,724	222,459
Inventory	326,843	289,066
Other current assets	144,600	215,822
Total current assets	2,975,427	2,540,420
Marketable securities	1,416,737	743,101
Property, plant and equipment, net	1,571,387	1,641,634
Intangible assets, net	1,608,191	1,772,826
Goodwill	1,146,314	1,146,314
Investments and other assets	331,548	248,198
Total assets	9,049,604	8,092,493
Current liabilities:
Current portion of notes payable, line of credit and other financing arrangements	3,292	137,153
Taxes payable	45,939	84,517
Accounts payable	186,448	162,529
Accrued expenses and other	677,210	665,923
Total current liabilities	912,889	1,050,122
Notes payable, line of credit and other financing arrangements	1,060,808	1,066,379
Long-term deferred tax liability	248,644	200,950
Other long-term liabilities	400,276	325,599
Total liabilities	2,622,617	2,643,050
Commitments and contingencies
Biogen Idec Inc. shareholders' equity
Preferred stock, par value $0.001 per share
Common stock, par value $0.0005 per share	128	124
Additional paid-in capital	4,185,048	3,895,103
Accumulated other comprehensive income (loss)	(26,535)	(21,610)
Retained earnings	3,106,761	1,872,481
Treasury stock, at cost; 13,518 shares and 7,662 shares, respectively	(839,903)	(349,592)
Total Biogen Idec Inc. shareholders' equity	6,425,499	5,396,506
Noncontrolling interests	1,488	52,937
Total equity	6,426,987	5,449,443
Total liabilities and equity	$ 9,049,604	$ 8,092,493