PENSION, PROFIT SHARING, AND OTHER EMPLOYEE BENEFIT PLANS (Additional Information) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets	5.00%	5.00%	6.00%
Maximum Percentage Of Asset Allocated To Control Market Volatility	more than 70%
Maximum Percentage Of Market Value For Initial Acquisition Of Equity Portion	not exceed 5%
Minimum Percentage Of Value Of Equity Portion For Sale	exceeds 10%
Maximum Percentage Of Corporate Debt Issuable To Single Issuer	not exceed 10%
Defined Benefit Plan, Contributions by Employer	$ 5,830	$ 0
Defined Benefit Plan, Investment Strategies, Investment Fund Category	Investment strategies and asset allocations are based on careful consideration of plan liabilities, the plan’s funded status and the Company’s financial condition. Investment performance and asset allocation are measured and monitored on an ongoing basis. The current target allocations for plan assets are 50-70% for equity securities, 30-40% for fixed income securities and 0-10% for cash equivalents. This asset allocation has been set after taking into consideration the Plan’s current frozen status and the possibility of partial plan terminations over the intermediate term. Market volatility risk is controlled by limiting the asset allocation of the most volatile asset class, equities, to no more than 70% of the portfolio and by ensuring that there is sufficient liquidity to meet distribution requirements from the portfolio without disrupting long-term assets. Diversification of the equity portion of the portfolio is controlled by limiting the value of any initial acquisition so that it does not exceed 5% of the market value of the portfolio when purchased. The policy requires the sale of any portion of an equity position when its value exceeds 10% of the portfolio. Fixed income market volatility risk is managed by limiting the term of fixed income investments to five years. Fixed income investments must carry an “A” or better rating by a recognized credit rating agency. Corporate debt of a single issuer may not exceed 10% of the market value of the portfolio. The investment in derivative instruments such as “naked” call options, futures, commodities, and short selling is prohibited. Investment in equity index funds and the writing of “covered” call options (a conservative strategy to increase portfolio income) are permitted. Foreign currency-denominated debt instruments are not permitted. At December 31, 2016, management is of the opinion that there are no significant concentrations of risk in the assets of the plan with respect to any single entity, industry, country, commodity or investment fund that are not otherwise mitigated by FDIC insurance available to the participants of the plan and collateral pledged for any such amount that may not be covered by FDIC insurance. Investment performance is measured against industry accepted benchmarks. The risk tolerance and asset allocation limitations imposed by the policy are consistent with attaining the rate of return assumptions used in the actuarial funding calculations. The RPIC committee meets quarterly to review the activities of the investment managers to ensure adherence with the Investment Policy Statement.
Four Zero One K Provision Description	The Sandy Spring Bank 401(k) Plan includes a 401(k) provision with a Company match. The 401(k) provision is voluntary and covers all eligible employees after ninety days of service. Employees contributing to the 401(k) provision receive a matching contribution of 100% of the first 3% of compensation and 50% of the next 2% of compensation subject to employee contribution limitations. The Company matching contribution vests immediately. The Plan permits employees to purchase shares of Sandy Spring Bancorp, Inc. common stock with their 401(k) contributions, Company match, and other contributions under the Plan.
Profit Sharing And Matching Contribution	$ 2,000	2,000	$ 1,800
Executive Incentive Retirement Plan Benefit Cost	$ 300	$ 200	$ 400
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Current target allocations for plan assets minimum	50.00%
Current target allocations for plan assets maximum	70.00%
Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Current target allocations for plan assets minimum	30.00%
Current target allocations for plan assets maximum	40.00%
Cash Funds And Emerging Market Debt Funds
Defined Benefit Plan Disclosure [Line Items]
Current target allocations for plan assets minimum	0.00%
Current target allocations for plan assets maximum	10.00%