| Document and Entity Information | Dec. 18, 2019 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001095996 |
| Document Type | 8-K |
| Document Period End Date | Dec. 18, 2019 |
| Entity Registrant Name | WILLIAM LYON HOMES |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-31625 |
| Entity Tax Identification Number | 33-0864902 |
| Entity Address, Address Line One | 4695 MacArthur Court |
| Entity Address, Address Line Two | 8th Floor |
| Entity Address, City or Town | Newport Beach |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92660 |
| City Area Code | (949) |
| Local Phone Number | 833-3600 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Class A Common Stock, $0.01 par value |
| Trading Symbol | WLH |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
