INVESTMENT SECURITIES - TRUST PREFERRED SECURITY (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Amortized cost and fair value of the investment securities portfolio by contractual maturity
Amount of floating rate purchased		$ 445,681	$ 173,875	$ 225,212
Trust preferred security
Amortized cost and fair value of the investment securities portfolio by contractual maturity
Amount of floating rate purchased	$ 3,000
Price as percentage of face value	68.00%
3 Month London Interbank Offered Rate (LIBOR) | Trust preferred security
Amortized cost and fair value of the investment securities portfolio by contractual maturity
Interest rate - Basis Spread	1.59%