Investment Securities - Schedule of Investment Securities' Gross Unrealized Losses and Fair Value by Investment Category (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair Value	$ 579,528	$ 394,889
Available-for-sale debt securities, Less than 12 months, Unrealized Loss	2,076	3,707
Available-for-sale debt securities, 12 months or longer, Fair Value	4,355	23,099
Available-for-sale debt securities, 12 months or longer, Unrealized Loss	3	275
Available-for-sale debt securities, Total, Fair Value	583,883	417,988
Available-for-sale debt securities, Total, Unrealized Loss	2,079	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	183,983	47,376
Available-for-sale debt securities, Less than 12 months, Unrealized Loss	443	481
Available-for-sale debt securities, 12 months or longer, Fair Value	0	7,999
Available-for-sale debt securities, 12 months or longer, Unrealized Loss	0	61
Available-for-sale debt securities, Total, Fair Value	183,983	55,375
Available-for-sale debt securities, Total, Unrealized Loss	443	542
FNMA MBS
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair Value	289,338	310,312
Available-for-sale debt securities, Less than 12 months, Unrealized Loss	879	2,681
Available-for-sale debt securities, 12 months or longer, Fair Value	4,355	6,522
Available-for-sale debt securities, 12 months or longer, Unrealized Loss	3	105
Available-for-sale debt securities, Total, Fair Value	293,693	316,834
Available-for-sale debt securities, Total, Unrealized Loss	882	2,786
FHLMC MBS
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair Value	5,191	35,354
Available-for-sale debt securities, Less than 12 months, Unrealized Loss	105	541
Available-for-sale debt securities, 12 months or longer, Fair Value	0	2,836
Available-for-sale debt securities, 12 months or longer, Unrealized Loss	0	50
Available-for-sale debt securities, Total, Fair Value	5,191	38,190
Available-for-sale debt securities, Total, Unrealized Loss	105	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
GSE agency notes
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair Value	101,016
Available-for-sale debt securities, Less than 12 months, Unrealized Loss	649
Available-for-sale debt securities, 12 months or longer, Fair Value	0
Available-for-sale debt securities, 12 months or longer, Unrealized Loss	0
Available-for-sale debt securities, Total, Fair Value	101,016
Available-for-sale debt securities, Total, Unrealized Loss	$ 649

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