CONDENSED FINANCIAL STATEMENTS OF PARENT COMPANY (Details 2) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income:
Total net revenue	$ 59,618,000	$ 49,538,000	$ 47,341,000	$ 40,947,000	$ 39,960,000	$ 41,712,000	$ 32,371,000	$ 28,280,000	$ 197,444,000	$ 142,323,000	$ 106,698,000
Interest expense	9,523,000	7,898,000	7,603,000	7,527,000	7,893,000	8,228,000	7,852,000	7,767,000	32,551,000	31,740,000	35,330,000
Income (loss) before income taxes and equity in undistributed income (loss) of subsidiaries	12,512,000	14,876,000	10,907,000	8,753,000	8,167,000	4,802,000	2,248,000	3,491,000	47,048,000	18,318,000	16,035,000
Income tax benefit	3,183,000	4,847,000	2,921,000	2,272,000	609,000	405,000	371,000	656,000	13,223,000	1,884,000	2,420,000
Net income (loss)	9,329,000	10,029,000	7,986,000	5,844,000	8,477,000	4,392,000	1,877,000	2,835,000	33,188,000	17,348,000	13,615,000
Berkshire Hills Bancorp
Income:
Dividends from subsidiaries									17,000,000	4,200,000
Other									481,000	11,000	10,000
Total net revenue									17,481,000	4,211,000	10,000
Interest expense									2,260,000	839,000	865,000
Operating expenses									3,988,000	4,119,000	1,426,000
Total expense									6,248,000	4,958,000	2,291,000
Income (loss) before income taxes and equity in undistributed income (loss) of subsidiaries									11,233,000	(747,000)	(2,281,000)
Income tax benefit									(2,277,000)	(2,028,000)	(930,000)
Income (loss) before equity in undistributed income (loss) of subsidiaries									13,510,000	1,281,000	(1,351,000)
Equity in undistributed income (loss) of subsidiaries									19,678,000	16,067,000	14,966,000
Net income (loss)									$ 33,188,000	$ 17,348,000	$ 13,615,000