Statements of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash Flows from Operating Activities:
Net income	$ 36,554	$ 34,102	$ 23,520
Adjustments to reconcile net income to net cash provided by operating activities:
Share based compensation expense	1,451	1,207	904
Net change in other liabilities	6,939	12,491	(3,040)
Other - net	3,954	5,893	4,948
Net cash provided by operating activities	52,790	67,710	56,647
Cash Flows from Investing Activities:
Purchases of investments available-for-sale	(264,993)	(370,657)	(725,641)
Acquisition of business activity, net of cash acquired	(849)	0	0
Net cash used by investing activities	(56,565)	(199,544)	83,281
Cash Flows from Financing Activities:
Redemption of preferred stock	0	0	(83,094)
Redemption of stock warrant	0	(4,449)	0
Proceeds from issuance of common stock	98	314	96,464
Tax benefit from stock options exercised	102	91	201
Repurchase of common stock	0	(334)	0
Dividends paid	(11,891)	(8,259)	(4,563)
Net cash provided (used) by financing activities	17,867	141,031	(136,607)
Net increase (decrease) in cash and cash equivalents	14,092	9,197	3,321
Cash and cash equivalents at beginning of period	72,314	63,117	59,796
Cash and cash equivalents at end of period	86,406	72,314	63,117
Sandy Spring Bancorp, Inc
Cash Flows from Operating Activities:
Net income	36,554	34,102	23,520
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed income-subsidiary	(25,285)	(13,305)	(24,013)
Dividends receivable from subsidiary bank		(13,000)	0
Share based compensation expense	1,451	1,207	904
Net change in other liabilities	(158)	(184)	43
Increase (Decrease) in Dividends Receivable	13,000
Other - net	(10,804)	(87)	14
Net cash provided by operating activities	14,758	8,733	468
Cash Flows from Investing Activities:
Purchases of investments available-for-sale	(511)	0	0
Acquisition of business activity, net of cash acquired	(849)	0	0
Net cash used by investing activities	(1,360)	0	0
Cash Flows from Financing Activities:
Redemption of preferred stock	0	0	(83,094)
Redemption of stock warrant	0	(4,449)	0
Proceeds from issuance of common stock	99	314	96,464
Tax benefit from stock options exercised	102	91	201
Repurchase of common stock	0	(334)	0
Dividends paid	(11,890)	(8,259)	(4,563)
Net cash provided (used) by financing activities	(11,689)	(12,637)	9,008
Net increase (decrease) in cash and cash equivalents	1,709	(3,904)	9,476
Cash and cash equivalents at beginning of period	8,326	12,230	2,754
Cash and cash equivalents at end of period	$ 10,035	$ 8,326	$ 12,230