INVESTMENT SECURITIES AVAILABLE FOR SALE - Amortized cost and fair value (Details) - USD ($)		12 Months Ended
	Oct. 04, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Amortized cost of available-for-sale securities, by contractual maturity
Within one year		$ 75,030,000
One to five years		105,597,000
Five to ten years		52,866,000
After ten years		14,032,000
Total, single maturity date		247,525,000
Amortized cost		247,525,000	$ 226,665,000
Fair Value of available-for-sale securities, by contractual maturity
Within one year		75,008,000
One to five years		105,344,000
Five to ten years		52,625,000
After ten years		13,362,000
Total, single maturity date		246,339,000
Available-for-sale Securities, Total		246,339,000	236,627,000
Available-for-sale Securities		246,339,000	236,627,000
Available-for-sale Securities, Gross Realized Gains		15,500,000	368,000	$ 173,000
Gross realized gains/losses
Gross realized gains		15,500,000	368,000	173,000
Gross realized losses		837,000	175,000	$ 96,000
Agency mortgage-backed securities
Amortized cost of available-for-sale securities, by contractual maturity
Amortized cost		90,629,000	66,902,000
Fair Value of available-for-sale securities, by contractual maturity
Available-for-sale Securities, Total		90,070,000	67,527,000
Available-for-sale Securities		90,070,000	67,527,000
Non-agency mortgage-backed securities
Amortized cost of available-for-sale securities, by contractual maturity
Amortized cost		1,000	2,000
Fair Value of available-for-sale securities, by contractual maturity
Available-for-sale Securities, Total		1,000	2,000
Available-for-sale Securities		$ 1,000	2,000
Covered non-agency mortgage-backed securities
Amortized cost of available-for-sale securities, by contractual maturity
Amortized cost			66,397,000
Fair Value of available-for-sale securities, by contractual maturity
Available-for-sale Securities, Total	$ 72,100,000		75,979,000
Available-for-sale Securities	72,100,000		$ 75,979,000
Available-for-sale Securities, Gross Realized Gains	14,300,000
Gross realized gains/losses
Gross realized gains	$ 14,300,000