INVESTMENTS - Schedule of Investment Securities' Gross Unrealized Losses and Fair Value by Investment Category (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair value	$ 2,568,846	$ 3,510,536
Available-for-sale debt securities, Less than 12 months, Unrealized loss	406,726	56,088
Available-for-sale debt securities, 12 months or longer, Fair value	1,571,392	550,108
Available-for-sale debt securities, 12 months or longer, Unrealized loss	379,766	23,109
Available-for-sale debt securities, Total, Fair value	4,140,238	4,060,644
Available-for-sale debt securities, Total, Unrealized loss	786,492	79,197
Held-to-maturity, Less than 12 months, Fair Value	1,033,370
Held-to-maturity, Less than 12 months, Unrealized Loss	80,734
Held-to-maturity, 12 months or longer, Fair Value	0
Held-to-maturity, 12 months or longer, Unrealized Loss	0
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	1,033,370
Held-to-maturity, Total, Unrealized Loss	80,734
Collateralized mortgage obligation (CMO)
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair value	199,644	411,347
Available-for-sale debt securities, Less than 12 months, Unrealized loss	20,982	12,730
Available-for-sale debt securities, 12 months or longer, Fair value	322,739	35,638
Available-for-sale debt securities, 12 months or longer, Unrealized loss	78,308	1,903
Available-for-sale debt securities, Total, Fair value	522,383	446,985
Available-for-sale debt securities, Total, Unrealized loss	99,290	14,633
FNMA MBS
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair value	2,232,612	3,018,606
Available-for-sale debt securities, Less than 12 months, Unrealized loss	369,840	41,021
Available-for-sale debt securities, 12 months or longer, Fair value	1,061,618	356,665
Available-for-sale debt securities, 12 months or longer, Unrealized loss	247,220	12,772
Available-for-sale debt securities, Total, Fair value	3,294,230	3,375,271
Available-for-sale debt securities, Total, Unrealized loss	617,060	53,793
Held-to-maturity, Less than 12 months, Fair Value	849,689
Held-to-maturity, Less than 12 months, Unrealized Loss	69,694
Held-to-maturity, 12 months or longer, Fair Value	0
Held-to-maturity, 12 months or longer, Unrealized Loss	0
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	849,689
Held-to-maturity, Total, Unrealized Loss	69,694
Freddie Mac (FHLMC) MBS
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair value	101,605	11,227
Available-for-sale debt securities, Less than 12 months, Unrealized loss	12,968	348
Available-for-sale debt securities, 12 months or longer, Fair value	8,036	1,917
Available-for-sale debt securities, 12 months or longer, Unrealized loss	2,406	168
Available-for-sale debt securities, Total, Fair value	109,641	13,144
Available-for-sale debt securities, Total, Unrealized loss	15,374	516
Ginnie Mae (GNMA) MBS
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair value	34,985	4,847
Available-for-sale debt securities, Less than 12 months, Unrealized loss	2,936	71
Available-for-sale debt securities, 12 months or longer, Fair value	1,751	0
Available-for-sale debt securities, 12 months or longer, Unrealized loss	427	0
Available-for-sale debt securities, Total, Fair value	36,736	4,847
Available-for-sale debt securities, Total, Unrealized loss	3,363	71
Government-sponsored enterprises (GSE) agency notes
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair value	0	64,509
Available-for-sale debt securities, Less than 12 months, Unrealized loss	0	1,918
Available-for-sale debt securities, 12 months or longer, Fair value	177,248	155,888
Available-for-sale debt securities, 12 months or longer, Unrealized loss	51,405	8,266
Available-for-sale debt securities, Total, Fair value	177,248	220,397
Available-for-sale debt securities, Total, Unrealized loss	51,405	$ 10,184
State and political subdivisions
Available-for-sale debt securities:
Held-to-maturity, Less than 12 months, Fair Value	183,181
Held-to-maturity, Less than 12 months, Unrealized Loss	11,039
Held-to-maturity, 12 months or longer, Fair Value	0
Held-to-maturity, 12 months or longer, Unrealized Loss	0
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	183,181
Held-to-maturity, Total, Unrealized Loss	11,039
Foreign bonds
Available-for-sale debt securities:
Held-to-maturity, Less than 12 months, Fair Value	500
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
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	500
Held-to-maturity, Total, Unrealized Loss	$ 1

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