| Document and Entity Information | Oct. 28, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 28, 2020 |
| Entity Registrant Name | Ryerson Holding Corporation |
| Entity Central Index Key | 0001481582 |
| Entity Emerging Growth Company | false |
| Entity File Number | 001-34735 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 26-1251524 |
| Entity Address, Address Line One | 227 W. Monroe St. |
| Entity Address, Address Line Two | 27th Floor |
| Entity Address, City or Town | Chicago |
| Entity Address, State or Province | IL |
| Entity Address, Postal Zip Code | 60606 |
| City Area Code | 312 |
| Local Phone Number | 292-5000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.01 par value, 100,000,000 shares authorized |
| Trading Symbol | RYI |
| Security Exchange Name | NYSE |
