| Cover Page | Aug. 09, 2019 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Aug. 8, 2019 |
| Entity Registrant Name | Alarm.com Holdings, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-37461 |
| Entity Tax Identification Number | 26-4247032 |
| Entity Address, Address Line One | 8281 Greensboro Drive |
| Entity Address, Address Line Two | Suite 100 |
| Entity Address, City or Town | Tysons |
| Entity Address, State or Province | VA |
| Entity Address, Postal Zip Code | 22102 |
| City Area Code | 877 |
| Local Phone Number | 389-4033 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.01 par value per share |
| Trading Symbol | ALRM |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0001459200 |
