SECURITIES - Additional Information (Details) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sale of Available-for-sale Securities, Debt	$ 39,408,000	$ 60,314,000
Available-for-sale Securities, Gross Realized Gains	448,000	632,000
Available-for-sale Securities, Gross Realized Losses	$ 87,000	$ 472,000
Collateral Underlying Mortgage Investments Terms	30- and 15-year fixed and 10/1 adjustable rate mortgage
Federal Home Loan Bank Stock and Federal Reserve Bank Stock	$ 30,900,000
Cost Method Investments, Fair Value Disclosure	30,900,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	340,150,000		$ 698,059,000
Accumulated unrealized losses	4,615,000		$ 12,703,000
Securities Available For Sale Transferred To Held-To-Maturity	28,700,000			$ 158,800,000
Available For Sale Securities Transferred To Held To Maturity Securities Unrealized Gain Loss	3,100,000			$ 3,100,000
Trading Securities, Unrealized Holding Loss	$ 1,900,000
Common Stock, Shares, Outstanding	38,025,020		34,351,409
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value			$ 38,900,000
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss			$ 400,000
Common Class B [Member]
Schedule of Available-for-sale Securities [Line Items]
Common Stock, Shares, Outstanding	11,330
Common Class A [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt Instrument, Convertible, Conversion Price	$ 1.6483
Stock Issued During Period, Shares, Conversion of Convertible Securities	18,675
Stock Issued During Period, Value, Conversion of Convertible Securities, Net of Adjustments, Total	$ 1,500,000
Available-for-sale Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	300,000
Securities Available For Sale Transferred To Held-To-Maturity	300,000
Carrying Amount [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities pledged as collateral	161,000,000
Carrying Amount [Member] | Repurchase Agreement [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities pledged as collateral	167,700,000
Mortgage Backed Securities And Collateralized Mortgage Obligations Of Us Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	180,500,000
Accumulated unrealized losses	0
Collateralized Loan Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Accumulated unrealized losses	1,100,000
Private Collateralized Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	79,500,000
Accumulated unrealized losses	$ 1,700,000