INVESTMENTS - Schedule of Investment Securities' Gross Unrealized Losses and Fair Value by Investment Category (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair Value	$ 8,469	$ 394,889
Available-for-sale debt securities, Less than 12 months, Unrealized Loss	50	3,707
Available-for-sale debt securities, 12 months or longer, Fair Value	826	23,099
Available-for-sale debt securities, 12 months or longer, Unrealized Loss	3	275
Available-for-sale debt securities, Total, Fair Value	9,295	417,988
Available-for-sale debt securities, Total, Unrealized Loss	53	3,982
Foreign bonds
Held-to-maturity debt securities:
Held-to-maturity, Less than 12 months, Fair Value		523
Held-to-maturity, Less than 12 months, Unrealized Loss		1
Held-to-maturity, 12 months or longer, Fair Value		0
Held-to-maturity, 12 months or longer, Unrealized Loss		0
Held-to-maturity, Total, Fair Value		523
Held-to-maturity, Total, Unrealized Loss		0
CMO
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair Value	4,044	47,376
Available-for-sale debt securities, Less than 12 months, Unrealized Loss	44	481
Available-for-sale debt securities, 12 months or longer, Fair Value	826	7,999
Available-for-sale debt securities, 12 months or longer, Unrealized Loss	3	61
Available-for-sale debt securities, Total, Fair Value	4,870	55,375
Available-for-sale debt securities, Total, Unrealized Loss	47	542
FNMA MBS
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair Value	4,425	310,312
Available-for-sale debt securities, Less than 12 months, Unrealized Loss	6	2,681
Available-for-sale debt securities, 12 months or longer, Fair Value	0	6,522
Available-for-sale debt securities, 12 months or longer, Unrealized Loss	0	105
Available-for-sale debt securities, Total, Fair Value	4,425	316,834
Available-for-sale debt securities, Total, Unrealized Loss	$ 6	2,786
FHLMC MBS
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair Value		35,354
Available-for-sale debt securities, Less than 12 months, Unrealized Loss		541
Available-for-sale debt securities, 12 months or longer, Fair Value		2,836
Available-for-sale debt securities, 12 months or longer, Unrealized Loss		50
Available-for-sale debt securities, Total, Fair Value		38,190
Available-for-sale debt securities, Total, Unrealized Loss		591
GNMA MBS
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair Value		1,847
Available-for-sale debt securities, Less than 12 months, Unrealized Loss		4
Available-for-sale debt securities, 12 months or longer, Fair Value		5,742
Available-for-sale debt securities, 12 months or longer, Unrealized Loss		59
Available-for-sale debt securities, Total, Fair Value		7,589
Available-for-sale debt securities, Total, Unrealized Loss		$ 63

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