UNAUDITED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS’ EQUITY - USD ($) $ in Thousands		Total	Common Stock	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Unallocated Common Stock Held by ESOP
Beginning balance (in shares) at Dec. 31, 2023			176,426,993
Beginning Balance at Dec. 31, 2023		$ 2,974,855	$ 1,767	$ 1,666,441	$ 2,047,754	$ (608,352)	$ (132,755)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common shareholders	[1]	(18,086)			(18,086)
Issuance of common stock under share-based compensation arrangements (in shares)	[2]		204,484
Issuance of common stock under share-based compensation arrangements	[2]	(1,262)	$ 2	(1,264)
Share-based compensation		3,589		3,589
Net income (loss)		38,647			38,647
Other comprehensive (loss) income , net of tax		(46,522)				(46,522)
ESOP shares committed to be released		1,610		367			1,243
Ending balance (in shares) at Mar. 31, 2024			176,631,477
Ending balance at Mar. 31, 2024		$ 2,952,831	$ 1,769	1,669,133	2,068,315	(654,874)	(131,512)
Beginning balance (in shares) at Dec. 31, 2024		213,909,472	213,909,472
Beginning Balance at Dec. 31, 2024		$ 3,611,967	$ 2,141	2,237,494	2,084,503	(584,329)	(127,842)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common shareholders	[1]	(24,230)			(24,230)
Repurchased common stock (in shares)			(2,875,530)
Repurchased common stock		(48,657)	$ (28)	(48,629)
Restricted share awards cancelled (in shares)	[3]		(10,435)
Restricted share awards cancelled	[3]	(139)	$ (2)	(137)
Issuance of common stock under share-based compensation arrangements (in shares)	[2]		536,670
Issuance of common stock under share-based compensation arrangements	[2]	(5,836)	$ 5	(5,841)
Share-based compensation		4,752		4,752
Net income (loss)		(217,666)			(217,666)
Other comprehensive (loss) income , net of tax		260,550				260,550
ESOP shares committed to be released		$ 2,193		913			1,280
Ending balance (in shares) at Mar. 31, 2025		211,560,177	211,560,177
Ending balance at Mar. 31, 2025		$ 3,582,934	$ 2,116	$ 2,188,552	$ 1,842,607	$ (323,779)	$ (126,562)

[1] The Company declared quarterly cash dividends of $0.12 and $0.11 per share of common stock during the three months ended March 31, 2025 and 2024, respectively.

[2] Represents shares issued, net of employee tax withheld, upon the vesting of performance and restricted stock units. Refer to Note 9, “Employee Benefits” for additional discussion.

[3] Includes 7,452 restricted stock award shares cancelled upon vesting for employee payroll tax withholding and 2,983 restricted stock award shares cancelled upon forfeiture. Shares withheld relate to awards issued by Cambridge Bancorp to its employees which were converted to awards of the Company upon completion of the Company' merger with Cambridge Bancorp effective July 12, 2024 (“the merger”).