ALLOWANCE FOR CREDIT LOSSES ON LOANS AND LEASES - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Percentage of growth, housing price index	4.70%		6.30%
Percentage of growth, commercial real estate price index	16.10%		13.00%
Percentage of growth (decline), S&P volatility in next fiscal year	(0.30%)		15.20%
Percentage of growth (decline), S&P volatility in next second year	(5.50%)		1.90%
Allowance for credit loss	$ 371.0		$ 344.0
Allowance for credit losses on loans and leases
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss	$ 370.6	$ 362.0	344.3	$ 363.0
Financing receivable, allowance for credit loss, period increase (decrease)			$ 26.4
Financing receivable, allowance for credit loss, period increase (decrease), percentage			7.70%
Financing receivable, allowance for credit loss, ratio	1.38%		1.38%
Financing receivable, allowance for credit loss, write-off, after recovery	$ (1.9)	$ (7.1)
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