| Cover | Nov. 03, 2020 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Nov. 3, 2020 |
| Entity File Number | 001-37949 |
| Entity Registrant Name | Innovative Industrial Properties, Inc. |
| Entity Central Index Key | 0001677576 |
| Entity Tax Identification Number | 81-2963381 |
| Entity Incorporation, State or Country Code | MD |
| Entity Address, Address Line One | 1389 Center Drive |
| Entity Address, Address Line Two | Suite 200 |
| Entity Address, City or Town | Park City |
| Entity Address, State or Province | UT |
| Entity Address, Postal Zip Code | 84098 |
| City Area Code | 858 |
| Local Phone Number | 997-3332 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Common Stock [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common Stock, par value $0.001 per share |
| Trading Symbol | IIPR |
| Security Exchange Name | NYSE |
| Series A Preferred Stock [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Series A Preferred Stock, par value $0.001 per share |
| Trading Symbol | IIPR-PA |
| Security Exchange Name | NYSE |
