COMMITMENTS AND CONTINGENCIES AND OTHER MATTERS (Detail Textuals) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments and Contingencies [Line Items]
Rental expenses under leases	$ 5,300	$ 3,400	$ 2,300
Securities sold under agreements to repurchase	50,891	$ 36,263
Bridgehampton National Bank
Commitments and Contingencies [Line Items]
Required cash balance with Federal Reserve Bank of New York	2,700
Average balance maintained	14,300
Lines of credit outstanding	120,000
Amount available for transactions under Master Repurchase Agreement	11,000,000
Bridgehampton National Bank | Overnight line of credit with the Federal Home Loan Bank of New York
Commitments and Contingencies [Line Items]
Lines of credit with unaffiliated correspondent banks to provide short-term credit	295,000
Lines of credit available on an unsecured basis	$ 275,000