INVESTMENTS - Narrative (Details)	1 Months Ended	3 Months Ended	9 Months Ended
	Jul. 31, 2021 USD ($)	Jun. 30, 2022 USD ($)	Sep. 30, 2022 USD ($) security	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Debt Securities, Available-for-sale [Line Items]
Trading securities			$ 0
Number of available for sale investment securities | security			964
Number of available-for-sale securities unrealized loss position | security			963
Weighted average duration of MBS portfolio			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			(149,600,000)
Sale of investment securities available for sale, including interest			0	14,000,000
Debt securities, available-for-sale, realized gain				300,000
Losses from sale of available-for-sale securities				0
Unamortized premiums			69,200,000		$ 69,400,000
Unaccreted discounts			26,400,000		12,700,000
Owned investment securities			5,200,000,000
Total unrealized losses on securities			867,200,000
Allowance for credit losses			0		0
Held-to-maturity debt securities with an amortized cost basis			1,100,000,000		90,600,000
Accrued interest			1,800,000		900,000
Debt securities nonaccrual			0		0
Equity investments			25,100,000		10,500,000
Equity securities net gains			6,000,000	$ 4,400,000
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
Allowance for credit losses			0		0
Common Class B
Debt Securities, Available-for-sale [Line Items]
Equity securities realized loss	$ (700,000)
Collateral Pledged
Debt Securities, Available-for-sale [Line Items]
Securities pledged as collateral			$ 2,900,000,000		$ 2,200,000,000