| Cover | Jan. 03, 2023 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Jan. 03, 2023 |
| Entity File Number | 001-40870 |
| Entity Registrant Name | MOUNT RAINIER ACQUISITION CORP. |
| Entity Central Index Key | 0001854461 |
| Entity Tax Identification Number | 86-2029991 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 256 W. 38th Street |
| Entity Address, Address Line Two | 15th Floor |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10018 |
| City Area Code | 212 |
| Local Phone Number | 785-4680 |
| Written Communications | true |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Elected Not To Use the Extended Transition Period | false |
| custom:Units [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Units |
| Trading Symbol | RNERU |
| Security Exchange Name | NASDAQ |
| Common Stock [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | RNER |
| Security Exchange Name | NASDAQ |
| custom:Warrants [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Warrants |
| Trading Symbol | RNERW |
| Security Exchange Name | NASDAQ |
