| Document and Entity Information | Nov. 07, 2019 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001397911 |
| Document Type | 8-K |
| Document Period End Date | Nov. 7, 2019 |
| Entity Registrant Name | LPL Financial Holdings Inc. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-34963 |
| Entity Tax Identification Number | 20-3717839 |
| Entity Address, Address Line One | Nos.) |
| Entity Address, Address Line Two | 75 State Street |
| Entity Address, City or Town | Boston |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02109 |
| City Area Code | (617) |
| Local Phone Number | 423-3644 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock - par value $0.001 per share |
| Trading Symbol | LPLA |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
