v2.4.0.6

Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended	9 Months Ended
	Jan. 31, 2012	Jun. 30, 2012	Sep. 30, 2012
Commitments [Abstract]
Commitment amount	$ 1.4	$ 3.0
Cacchillo v. Insmed [Abstract]
Number of claims dismissed			6
Number of claims for which motion for summary judgment filed			3
Pilkiewicz v. Transave LLC [Abstract]
Number of shares under appraisal of combined common stock holdings of Transave (in shares)		7.77	1.76

X

- Details

Name:	insm_CacchilloVInsmedAbstract
Namespace Prefix:	insm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	insm_CommitmentsAbstract
Namespace Prefix:	insm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

This line item represents the number of claims for which motion for summary judgment filed by the entity.

+ References

No definition available.

+ Details

Name:	insm_NumberOfClaimsForWhichMotionForSummaryJudgmentFiled
Namespace Prefix:	insm_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Number of shares under appraisal of combined common stock holdings.

+ References

No definition available.

+ Details

Name:	insm_NumberOfSharesUnderAppraisalOfCombinedCommonStockHoldings
Namespace Prefix:	insm_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	insm_PilkiewiczVTransaveLlcAbstract
Namespace Prefix:	insm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The minimum amount the entity agreed to spend under the long-term purchase commitment.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermPurchaseCommitmentAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

The number of claims settled and dismissed during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9, 10, 11, 12

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_LossContingencyClaimsSettledAndDismissedNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration