| Cover Page | Apr. 29, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Apr. 29, 2021 |
| Entity Registrant Name | ALLIANCEBERNSTEIN L.P. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 000-29961 |
| Entity Tax Identification Number | 13-4064930 |
| Entity Address, Address Line One | 1345 Avenue of the Americas |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10105 |
| City Area Code | 212 |
| Local Phone Number | 969-1000 |
| 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 | 0001109448 |
| Amendment Flag | false |
