INVESTMENTS - Narrative (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($) security	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) security	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Debt Securities, Available-for-sale [Line Items]
Trading securities	$ 0		$ 0
Number of available for sale investment securities | security	960		960
Number of available-for-sale securities unrealized loss position | security	936		936
Weighted average duration of MBS portfolio	6 years		6 years
Securities transferred to held-to-maturity from available-for-sale at fair value			$ 931,421,000	$ 0
Available for sale securities transfers to held to maturity unrealized (losses) gains	$ (157,400,000)		(157,400,000)
Sale of investment securities available for sale, including interest			0	9,300,000
Debt securities, available-for-sale, realized gain			0	300,000
Losses from sale of available-for-sale securities			0	0
Unamortized premiums	66,700,000		66,700,000		$ 69,400,000
Unaccreted discounts	26,600,000		26,600,000		12,700,000
Owned investment securities	4,400,000,000		4,400,000,000
Total unrealized losses on securities	521,600,000		521,600,000
Allowance for credit losses	0		0		0
Held-to-maturity debt securities with an amortized cost basis	1,100,000,000		1,100,000,000		90,600,000
Accrued interest	1,000,000		1,000,000		900,000
Debt securities nonaccrual	0		0		0
Equity investments	21,100,000		21,100,000		10,500,000
Unrealized gain (loss) on equity investments, net	5,991,000	$ 5,261,000	5,988,000	5,261,000
Unrealized gain		$ 5,100,000		$ 5,100,000
Fannie Mae (FNMA) mortgage-backed securities (MBS)
Debt Securities, Available-for-sale [Line Items]
Securities transferred to held-to-maturity from available-for-sale, book value	1,100,000,000
Securities transferred to held-to-maturity from available-for-sale at fair value	931,400,000
Available for sale securities transfers to held to maturity unrealized (losses) gains	157,600,000		157,600,000
Common Class B
Debt Securities, Available-for-sale [Line Items]
Unrealized gain	200,000		200,000
Collateral Pledged
Debt Securities, Available-for-sale [Line Items]
Securities pledged as collateral	$ 2,500,000,000		$ 2,500,000,000		$ 2,200,000,000