Amortization and Impairment of Acquired Intangible Assets

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- Definition

Manufacturing and Other Costs

+ References

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- Definition

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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- Definition

Fair value portion of assets, excluding financial assets, that lack physical substance, having a limited useful life.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
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- Definition

Amount of accumulated impairment loss for an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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- Definition

Amount of impairment loss resulting from write-down of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value.

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- Definition

Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.

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Intangible Assets and Goodwill - Narrative (Details) - USD ($)	3 Months Ended				12 Months Ended
	Sep. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Line Items]
Amortization and impairment of acquired intangible assets					$ 881,300,000	$ 464,800,000	$ 489,900,000
Amortization of acquired intangible assets					252,000,000	255,100,000	274,000,000
Accumulated impairment losses related to goodwill					0
In-process research and development
Goodwill [Line Items]
Impairment of intangible assets				$ 215,900,000
Intangible assets (excluding goodwill)			$ 762,500,000		132,700,000	762,500,000
Intangible asset, fair value			0	$ 0		0
BIIB111
Goodwill [Line Items]
Impairment of intangible assets					365,000,000	115,000,000
BIIB111 \| In-process research and development
Goodwill [Line Items]
Intangible asset, fair value	$ 0				0
BIIB112
Goodwill [Line Items]
Impairment of intangible assets	220,000,000
BIIB112 \| In-process research and development
Goodwill [Line Items]
Intangible asset, fair value	0				0
BIIB054
Goodwill [Line Items]
Impairment of intangible assets						75,400,000
In Process Research and Development Other
Goodwill [Line Items]
Impairment of intangible assets						19,300,000
BG00011
Goodwill [Line Items]
Impairment of intangible assets							$ 215,900,000
TGN \| In-process research and development
Goodwill [Line Items]
Impairment of intangible assets		$ 44,300,000
DPN \| In-process research and development
Goodwill [Line Items]
Intangible assets (excluding goodwill)					132,700,000
BIIB111 and BIIB112
Goodwill [Line Items]
Manufacturing and other costs					39,100,000
Nightstar \| BIIB111
Goodwill [Line Items]
Impairment of intangible assets	$ 365,000,000
Intangible assets (excluding goodwill)					0
Nightstar \| BIIB111 \| In-process research and development
Goodwill [Line Items]
Impairment of intangible assets			115,000,000
Nightstar \| BIIB112
Goodwill [Line Items]
Impairment of intangible assets					220,000,000
Intangible assets (excluding goodwill)					$ 0
Nightstar \| BIIB054
Goodwill [Line Items]
Impairment of intangible assets			75,400,000
Intangible asset, fair value			$ 0			$ 0