| Document and Entity Information | Nov. 06, 2019 |
| Document And Entity Information [Line Items] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001692819 |
| Document Type | 8-K |
| Document Period End Date | Nov. 6, 2019 |
| Entity Registrant Name | VISTRA ENERGY CORP. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-38086 |
| Entity Tax Identification Number | 36-4833255 |
| Entity Address, Address Line One | 6555 Sierra Drive |
| Entity Address, City or Town | Irving |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 75039 |
| City Area Code | (214) |
| Local Phone Number | 812-4600 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Common Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Common stock, par value $0.01 per share |
| Trading Symbol | VST |
| Security Exchange Name | NYSE |
| Warrant [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Warrants |
| Trading Symbol | VST.WS.A |
| Security Exchange Name | NYSE |
