INVESTMENTS - FHLB (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Investment in common stock	$ 10,590,831	$ 8,208,566
Investment in FHLB
Schedule of Investments [Line Items]
Investment in common stock	137,760	137,760
Funding agreements issued to FHLB member banks	2,556,464	2,566,410
Collateral	3,793,974	4,135,612
FHLB Indianapolis | Investment in FHLB
Schedule of Investments [Line Items]
Investment in common stock	80,640	80,640
Funding agreements issued to FHLB member banks	1,612,765	1,619,765
Collateral	2,423,183	2,577,698
FHLB Des Moines | Investment in FHLB
Schedule of Investments [Line Items]
Investment in common stock	34,600	34,600
Funding agreements issued to FHLB member banks	619,532	620,006
Collateral	902,358	1,004,530
FHLB Boston | Investment in FHLB
Schedule of Investments [Line Items]
Investment in common stock	22,520	22,520
Funding agreements issued to FHLB member banks	324,167	326,639
Collateral	$ 468,433	$ 553,384