ALLOWANCE FOR CREDIT LOSSES ON LOANS AND LEASES - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Jan. 22, 2022	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Percentage of growth, housing price index		6.00%		6.00%			6.30%
Percentage of growth, commercial real estate price index		11.40%		11.40%			13.00%
Percentage of growth (decline), S&P volatility in next fiscal year		2.30%		2.30%			15.20%
Percentage of growth (decline), S&P volatility in next second year		(8.60%)		(8.60%)			1.90%
Allowance for credit loss		$ 378.0		$ 378.0			$ 344.0
Provision for credit losses		6.0	$ (1.0)	24.0	$ 5.0
Allowance for credit losses on loans and leases
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss		$ 378.0	357.0	378.0	357.0	$ 370.6	$ 344.3	$ 362.0	$ 363.0
Financing receivable, allowance for credit loss, period increase (decrease)				$ 33.7
Financing receivable, allowance for credit loss, period increase (decrease), percentage				9.80%
Financing receivable, allowance for credit loss, ratio		1.35%		1.35%			1.38%
Provision for credit losses		$ 7.0	(1.0)	$ 25.2	5.0
Financing receivable, allowance for credit loss, write-off, after recovery (charge-off)		0.4	(3.8)	(1.5)	(11.0)
Allowance for credit losses on loans and leases | Howard
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing receivable, non-purchased credit deterioration loans, allowance for credit loss at acquisition date, provision	$ 19.1			19.1
Allowance for credit losses on loans and leases and allowance for unfunded loan commitments
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss		396.2	371.0	396.2	371.0	$ 389.4	$ 363.4	$ 376.0	$ 377.0
Provision for credit losses		6.4	(1.0)	24.3	5.0
Financing receivable, allowance for credit loss, write-off, after recovery (charge-off)		$ 0.4	$ (4.0)	$ (1.5)	$ (11.0)