Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Balance beginning of period at Dec. 31, 2022	$ 992,125	$ 852	$ 736,074	$ 412,019	$ (61,947)	$ (94,873)
Increase (Decrease) in Stockholders' Equity
Net income	74,999			74,999
PCSB acquisition	167,330	118	167,212
Other comprehensive income (loss)	9,149				9,149
Common stock dividends	(47,926)			(47,926)
Restricted stock awards, net of awards surrendered	(756)		(4,720)			3,964
Compensation under recognition and retention plans	3,723		4,093	(370)
Balance end of period at Dec. 31, 2023	1,198,644	970	902,659	438,722	(52,798)	(90,909)
Increase (Decrease) in Stockholders' Equity
Net income	68,715			68,715
PCSB acquisition		0
Other comprehensive income (loss)	(84)				(84)
Common stock dividends	(48,058)			(48,058)
Restricted stock awards, net of awards surrendered	(658)		(3,891)			3,233
Compensation under recognition and retention plans	3,380		3,816	(436)
Balance end of period at Dec. 31, 2024	1,221,939	970	902,584	458,943	(52,882)	(87,676)
Increase (Decrease) in Stockholders' Equity
Net income	90,271			90,271
Impact of Merger between Brookline and Berkshire	1,214,996	(74)	1,268,308	82		(53,320)
PCSB acquisition		0
Other comprehensive income (loss)	32,880				32,880
Common stock dividends	(63,119)			(63,119)
Restricted stock awards, net of awards surrendered	(7,063)		(5,226)			(1,837)
Options exercised	238			(15)		253
Compensation under recognition and retention plans	5,919		6,219	(300)
Balance end of period at Dec. 31, 2025	$ 2,496,061	$ 896	$ 2,171,885	$ 485,862	$ (20,002)	$ (142,580)