SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Detail) - USD ($) $ in Millions		12 Months Ended
	Jan. 01, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in stockholders' equity attributable to parent		$ 5,653.0	$ 5,150.0	$ 4,959.0	$ 4,883.0
Financing receivable, allowance for credit loss, period increase (decrease)	$ 105.0
Allowance for credit loss		$ 402.0	344.0
Initial ACL on PCD Loans	50.3
Core deposit intangibles amortization period, years		10 years
Operating lease, right-of-use asset, statement of financial position [extensible enumeration]		Other assets
Operating lease, liability, statement of financial position [extensible enumeration]		Other liabilities
Finance lease right-of-use asset, statement of financial position [extensible enumeration]		Premises and equipment, net
Finance lease, liability, statement of financial position [extensible enumeration]		Other liabilities
Largest amount recognized in the financial statement of tax benefit threshold, minimum		50.00%
Non-Employee Directors
Summary Of Significant Accounting Policies [Line Items]
Vesting period of awards issued, years		1 year
Restricted Stock Units (RSUs)
Summary Of Significant Accounting Policies [Line Items]
Vesting period of awards issued, years		3 years
Minimum
Summary Of Significant Accounting Policies [Line Items]
Useful life of the asset, years		3 years
Estimated useful life of intangibles, years		8 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Useful life of the asset, years		39 years
Estimated useful life of intangibles, years		13 years
Commercial Loan
Summary Of Significant Accounting Policies [Line Items]
Threshold period past due for non-accrual loans		90 days
Commercial Loan | Minimum
Summary Of Significant Accounting Policies [Line Items]
Financing receivable, individual reserves in default, threshold		$ 1.0
Installment Loans
Summary Of Significant Accounting Policies [Line Items]
Threshold period past due for non-accrual loans		120 days
Residential Mortgages and Consumer Lines of Credit
Summary Of Significant Accounting Policies [Line Items]
Threshold period past due for non-accrual loans		180 days
Commercial and Consumer Loans | Maximum
Summary Of Significant Accounting Policies [Line Items]
Financing receivable, individual reserves in default, threshold		$ 1.0
Retained Earnings
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in stockholders' equity attributable to parent		$ 1,370.0	$ 1,110.0	$ 869.0	$ 798.0
Accounting Standards Update 2016-13 | Longer duration loans and gross up
Summary Of Significant Accounting Policies [Line Items]
Financing receivable, allowance for credit loss, period increase (decrease)	50.0
Accounting Standards Update 2016-13 | Unfunded loan commitment
Summary Of Significant Accounting Policies [Line Items]
Allowance for credit loss	10.0
ASC 326 Adoption Impact | Accounting Standards Update 2016-13 | Retained Earnings
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in stockholders' equity attributable to parent	$ (50.6)