License and Collaborative Agreements (Details) (Premacure License Agreement, USD $) In Millions, unless otherwise specified	1 Months Ended
Mar. 31, 2013	Apr. 29, 2013
Premacure License Agreement
License and Collaborative Agreements
License purchase option price	$ 11.5
Proceeds from sale of license		$ 11.5

Represents the amount received by the entity in sale of a fully paid license related to the entity's product(s).

No definition available.

Name:	insm_ProceedsFromSaleOfLicense
Namespace Prefix:	insm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant