| Cover | Feb. 25, 2021 |
| Cover [Abstract] | |
| Document Period End Date | Feb. 25, 2021 |
| Document Type | 8-K |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38352 |
| Entity Tax Identification Number | 47-4116383 |
| Entity Address, Address Line One | 1501 Yamato Road |
| Entity Address, City or Town | Boca Raton |
| Entity Address, State or Province | FL |
| Entity Address, Postal Zip Code | 33431 |
| City Area Code | 561 |
| Local Phone Number | 988-3600 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Trading Symbol | ADT |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Entity Central Index Key | 0001703056 |
| Amendment Flag | false |
| Entity Registrant Name | ADT Inc. |
