CONDENSED FINANCIAL STATEMENTS OF PARENT COMPANY - Schedule of CONDENSED STATEMENTS OF OPERATIONS (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
Income:
Total net revenue	$ 80,038	$ 107,799	$ 109,853	$ 114,139	$ 117,746	$ 108,335	$ 97,709	$ 89,744	$ 411,829	$ 413,534	$ 434,414
Interest expense	62,116	57,687	52,666	34,783	19,292	11,587	6,021	5,760	207,252	42,660	37,899
Income tax (benefit)	(4,509)	3,741	3,944	5,548	5,227	4,941	6,119	4,998	8,724	21,285	30,357
Net income/(loss)	$ (1,445)	$ 19,545	$ 23,861	$ 27,637	$ 30,505	$ 18,717	$ 23,115	$ 20,196	69,598	92,533	118,664
Comprehensive income/(loss)									107,634	(85,276)	84,550
Reportable legal entity | Berkshire Hills Bancorp
Income:
Dividends from subsidiaries									62,000	108,000	118,000
Other									50	23	31
Total net revenue									62,050	108,023	118,031
Interest expense									5,697	7,044	5,393
Non-interest expenses									3,702	2,754	2,719
Total expense									9,399	9,798	8,112
Income before income taxes and equity in undistributed income of subsidiaries									52,651	98,225	109,919
Income tax (benefit)									(2,500)	(2,586)	(2,136)
Income before equity in undistributed income of subsidiaries									55,151	100,811	112,055
Equity in undistributed results of operations of subsidiaries									14,447	(8,278)	6,609
Net income/(loss)									69,598	92,533	118,664
Comprehensive income/(loss)									$ 107,634	$ (85,276)	$ 84,550