CONDENSED FINANCIAL STATEMENTS OF PARENT COMPANY (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Assets
Cash due from Berkshire Bank	$ 54,179,000	$ 56,841,000
Other assets	61,090,000	54,009,000
Total assets	6,502,031,000	5,672,799,000
Liabilities and Stockholders' Equity
Short-term debt	900,900,000	872,510,000
Subordinated notes	89,747,000	89,679,000
Stockholders' equity	709,287,000	678,062,000	667,265,000	551,808,000
Total liabilities and stockholders' equity	6,502,031,000	5,672,799,000
Reportable legal entity | Berkshire Hills Bancorp
Condensed balance sheets
Intercompany subordinated notes	35,000,000
Assets
Cash due from Berkshire Bank	30,533,000	40,154,000
Investment in subsidiaries	736,908,000	698,943,000
Other assets	43,023,000	41,489,000
Total assets	810,464,000	780,586,000
Liabilities and Stockholders' Equity
Short-term debt	10,000,000	10,000,000
Subordinated notes	89,748,000	89,680,000
Accrued expenses	1,429,000	2,844,000
Stockholders' equity	709,287,000	678,062,000
Total liabilities and stockholders' equity	$ 810,464,000	$ 780,586,000