| Document And Entity Information | Feb. 02, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Feb. 2, 2021 |
| Entity Registrant Name | 1ST CONSTITUTION BANCORP |
| Entity Incorporation, State or Country Code | NJ |
| Entity File Number | 000-32891 |
| Entity Tax Identification Number | 22-3665653 |
| Entity Address, Address Line One | 2650 Route 130 |
| Entity Address, Address Line Two | P.O. Box 634 |
| Entity Address, City or Town | Cranbury |
| Entity Address, State or Province | NJ |
| Entity Address, Postal Zip Code | 08512 |
| City Area Code | 609 |
| Local Phone Number | 655-4500 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock, no par value |
| Trading Symbol | FCCY |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001141807 |
| Amendment Flag | false |
