INVESTMENT SECURITIES - Available-for-sale Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 626,064	$ 623,037
Gross Unrealized Gains	10,292	3,666
Gross Unrealized Losses	(1,032)	(1,629)
Estimated Fair Value	635,324	625,074
Fair Value
Less than 12 Months	113,051	169,044
12 Months or More	79,270	199,494
Total	192,321	368,538
Unrealized Losses
Less than 12 Months	(499)	(606)
12 Months or More	(533)	(1,023)
Total	(1,032)	(1,629)
Residential mortgage backed securities ('MBS") and collateralized mortgage obligations ("CMOs")
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	258,137	145,333
Gross Unrealized Gains	3,639	340
Gross Unrealized Losses	(159)	(481)
Estimated Fair Value	261,617	145,192
Fair Value
Less than 12 Months	19,570	43,623
12 Months or More	19,713	54,870
Total	39,283	98,493
Unrealized Losses
Less than 12 Months	(111)	(181)
12 Months or More	(48)	(300)
Total	(159)	(481)
Commercial MBS and CMOs
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	352,247	353,727
Gross Unrealized Gains	6,594	3,267
Gross Unrealized Losses	(830)	(825)
Estimated Fair Value	358,011	356,169
Fair Value
Less than 12 Months	80,844	95,950
12 Months or More	59,557	57,219
Total	140,401	153,169
Unrealized Losses
Less than 12 Months	(345)	(339)
12 Months or More	(485)	(486)
Total	(830)	(825)
Agency bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	15,680	123,977
Gross Unrealized Gains	59	59
Gross Unrealized Losses	(43)	(323)
Estimated Fair Value	15,696	123,713
Fair Value
Less than 12 Months	12,637	29,471
12 Months or More	0	87,405
Total	12,637	116,876
Unrealized Losses
Less than 12 Months	(43)	(86)
12 Months or More	0	(237)
Total	$ (43)	$ (323)