| Document and Entity Information | May 10, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | May 10, 2021 |
| Entity Registrant Name | INSMED INCORPORATED |
| Entity Incorporation, State or Country Code | VA |
| Entity File Number | 000-30739 |
| Entity Tax Identification Number | 54-1972729 |
| Entity Address, Address Line One | 700 US Highway 202/206 |
| Entity Address, City or Town | Bridgewater |
| Entity Address, State or Province | NJ |
| Entity Address, Postal Zip Code | 08807 |
| City Area Code | 908 |
| Local Phone Number | 977-9900 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001104506 |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | INSM |
| Security Exchange Name | NASDAQ |
