ACQUISITION OF REVERE BANK - Provisional fair values of acquired identifiable assets and liabilities assumed (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended	6 Months Ended
	Apr. 01, 2020	Jun. 30, 2020	Jun. 30, 2020
Purchase price:
Fair value of common shares issued (12,768,949 shares) based on Sandy Spring's share price of $22.64	$ 289,089	$ 289,089	$ 289,089
Fair value of Revere stock options converted to Sandy Spring stock options	3,611	$ 3,611	$ 3,611
Cash paid for cashed-out Revere stock options	291
Cash for fractional shares	11
Total purchase price	293,002
Identifiable assets and liabilities acquired:
Cash and cash equivalents	80,768
Investments available-for-sale	180,752
Loans	2,502,244
Premises and equipment	3,443
Accrued interest receivable	7,651
Core deposit intangible asset	18,360
Other assets	52,812
Total identifiable assets	2,846,030
Deposits	2,322,422
Borrowings	205,514
Other liabilities	25,931
Total identifiable liabilities	2,553,867
Provisional fair value of net assets acquired including identifiable intangible assets	292,163
Provisional resulting goodwill	$ 839
Stock issued in connection with Revere bank aquisition	12,768,949	12,768,949	12,768,949
Share price	$ 22.64