Unaudited Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2020 |
Mar. 31, 2019 |
|
| Statement of Comprehensive Income [Abstract] | ||
| Net (loss) income before noncontrolling interest in subsidiary | $ (17,276) | $ 22,510 |
| Investment securities available-for-sale: | ||
| Unrealized securities holding gains (losses) | 18,810 | 6,500 |
| Income tax (expense) benefit | (4,146) | (1,433) |
| Net unrealized securities holding gains (losses) before reclassification adjustments, net of taxes | 14,664 | 5,067 |
| Net unrealized securities holding gains (losses) | 14,664 | 5,067 |
| Other comprehensive (loss) income, net of taxes | 14,664 | 5,067 |
| Comprehensive (loss) income | (2,612) | 27,577 |
| Less: net income attributable to noncontrolling interest in subsidiary | 0 | 43 |
| Comprehensive (loss) income attributable to Brookline Bancorp, Inc. | $ (2,612) | $ 27,534 |