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SUBSEQUENT EVENT (Details) $ / shares in Units, $ in Millions | Feb. 01, 2021 USD ($) $ / shares shares | Dec. 31, 2020 $ / shares shares | Dec. 31, 2019 $ / shares shares | Sep. 30, 2015 USD ($)
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Subsequent Event [Line Items] |  |  |  |
Common stock, par value (in dollars per share) |  | $ 0.01 | $ 0.01 |
Common stock issued to Legacy Dime shareholders in connection with the Merger | shares |  | 19,951,955 | 19,898,022 |
Preferred stock, par value (in dollars per share) |  | $ 0.01 | $ 0.01 |
Preferred stock, shares issued | shares |  | 0 | 0 |
Aggregate principal amount of 4.50% Fixed-to-Floating Rate Debentures due 2027 | $ |  |  |  | $ 80.0
Subsequent Event |  |  |  |
Subsequent Event [Line Items] |  |  |  |
Common stock, par value (in dollars per share) | $ 0.01 |  |  |
Share conversion ratio | 0.6480 |  |  |
Subsequent Event | Legacy Dime |  |  |  |
Subsequent Event [Line Items] |  |  |  |
Common stock, par value (in dollars per share) | $ 0.01 |  |  |
Common stock issued to Legacy Dime shareholders in connection with the Merger | shares | 21,232,920 |  |  |
Preferred stock, par value (in dollars per share) | $ 0.01 |  |  |
Subsequent Event | Subordinated Debentures | Legacy Dime |  |  |  |
Subsequent Event [Line Items] |  |  |  |
Aggregate principal amount of 4.50% Fixed-to-Floating Rate Debentures due 2027 | $ | $ 115.0 |  |  |
Fixed interest rate of debentures | 4.50% |  |  |
Preferred Stock | Subsequent Event |  |  |  |
Subsequent Event [Line Items] |  |  |  |
Share conversion ratio | 1 |  |  |
Non-Cumulative Perpetual Preferred Stock, Series A | Subsequent Event |  |  |  |
Subsequent Event [Line Items] |  |  |  |
Preferred stock, shares issued | shares | 5,299,200 |  |  |
Preferred stock fixed-rate | 5.50% |  |  |

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