REGULATORY CAPITAL AND DIVIDENDS - Narrative (Details)		12 Months Ended
	Apr. 01, 2022 $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($)	Jan. 27, 2021 USD ($) shares	Nov. 01, 2013 USD ($) investor
Restructuring Cost and Reserve [Line Items]
Private debt issuance, number of institutional investors | investor						4
Debt face amount						$ 70,000,000
Repayment of borrowings		$ 1,119,200,000	$ 1,332,889,000	$ 96,204,000
Dividends available		305,900,000
Dividend reinvestment and stock purchase plan, stockholder's maximum amount of cash payments per quarter in purchase of common stock		$ 5,000
Cash dividends on preferred stock (in dollars per share) | $ / shares		$ 187.52	$ 140.64
Cash dividends on preferred stock		$ 1,875,000	$ 1,406,000
Stock Repurchase Program
Restructuring Cost and Reserve [Line Items]
Stock authorized to be repurchased (in shares) | shares					3,333,000
Stock authorized to be repurchased (in shares)					$ 100,000,000
Percent of outstanding shares					6.00%
Available to repurchase (in shares) | shares			2,700,000
Available to repurchase			$ 74,500,000
Series A Preferred Stock
Restructuring Cost and Reserve [Line Items]
Preferred Stock, issued (in shares) | shares		10,000	10,000
Liquidation value per share (in dollars per share) | $ / shares		$ 2,500	$ 2,500
Cash dividends on preferred stock (in dollars per share) | $ / shares		187.52	140.64
Depository share dividends (in dollars per share) | $ / shares		$ 1.88	$ 1.41
Cash dividends on preferred stock		$ 1,900,000	$ 1,400,000
Series A Preferred Stock | Level One
Restructuring Cost and Reserve [Line Items]
Preferred Stock, issued (in shares) | shares	10,000
Dividend rate, percentage	7.50%
Liquidation value per share (in dollars per share) | $ / shares	$ 2,500
Outstanding preferred stock			$ 25,000,000
Senior Notes
Restructuring Cost and Reserve [Line Items]
Private debt issuance, number of institutional investors | investor						4
Debt face amount						$ 70,000,000
Phase out period		5 years
Phase out annual percent		20.00%
Phase out annual amount		$ 13,000,000
Senior Notes | Fixed-to-Floating Rate Senior Notes due 2028
Restructuring Cost and Reserve [Line Items]
Debt face amount						$ 5,000,000
Interest rate on notes (as a percent)						5.00%
Senior Notes | Fixed-to-Floating Rate Subordinated Notes due 2028
Restructuring Cost and Reserve [Line Items]
Debt face amount						$ 65,000,000
Interest rate on notes (as a percent)						6.75%