CONDENSED FINANCIAL STATEMENTS OF PARENT COMPANY - Schedule of CONDENSED STATEMENTS OF CASH FLOWS (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net income	$ (1,445)	$ 19,545	$ 23,861	$ 27,637	$ 30,505	$ 18,717	$ 23,115	$ 20,196	$ 69,598	$ 92,533	$ 118,664
Adjustments to reconcile net income to net cash provided by operating activities:
Other, net									14,387	(12,076)	18,282
Net cash provided by operating activities									157,156	110,739	84,788
Cash flows from investing activities:
Net cash (used)/provided by investing activities									(284,461)	(1,260,886)	621,243
Cash flows from financing activities:
Proceeds from issuance of long term debt									0	98,032	0
Payment to repurchase common stock									(23,844)	(124,519)	(68,712)
Common and preferred stock cash dividends paid									(31,707)	(24,527)	(24,553)
Net cash provided/(used) by financing activities									645,194	207,695	(636,099)
Net change in cash and cash equivalents									517,889	(942,452)	69,932
Cash and cash equivalents at beginning of year				685,355				1,627,807	685,355	1,627,807	1,557,875
Cash and cash equivalents at end of year	1,203,244				685,355				1,203,244	685,355	1,627,807
Reportable legal entity | Berkshire Hills Bancorp
Cash flows from operating activities:
Net income									69,598	92,533	118,664
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed results of operations of subsidiaries									(14,447)	8,278	(6,609)
Other, net									8,688	5,998	5,816
Net cash provided by operating activities									63,839	106,809	117,871
Cash flows from investing activities:
Sale of securities									0	0	167
Net cash (used)/provided by investing activities									0	0	167
Cash flows from financing activities:
Proceeds from issuance of short term debt									0	0	232
Repayment of long term debt									0	(75,000)	0
Payment to repurchase common stock									(23,844)	(124,519)	(68,712)
Common and preferred stock cash dividends paid									(31,707)	(24,527)	(24,553)
Other, net									142	281	431
Net cash provided/(used) by financing activities									(55,409)	(125,733)	(92,602)
Net change in cash and cash equivalents									8,430	(18,924)	25,436
Cash and cash equivalents at beginning of year				$ 90,022				$ 108,946	90,022	108,946	83,510
Cash and cash equivalents at end of year	$ 98,452				$ 90,022				$ 98,452	$ 90,022	$ 108,946