FAIR VALUE - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	$ 4,647,019	$ 2,123,525
Fair Value, Measurements, Recurring [Member]
Assets Fair Value Disclosure [Abstract]
Equity Securities, FV-NI	1,474	1,428
Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	1,622	0
Derivative Liabilities [Abstract]
Derivative Liabilities	1,639	0
Fair Value, Measurements, Recurring [Member] | Other Available For Sale Securities [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	650	500
Fair Value, Measurements, Recurring [Member] | U S Treasury Securities [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	7,507	7,479
Fair Value, Measurements, Recurring [Member] | Government Agencies Debt Securities [Member] | Noncallable [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	173,371	146,777
Fair Value, Measurements, Recurring [Member] | Government Agencies Debt Securities [Member] | Call Option [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	4,454,164	1,950,331
Fair Value, Measurements, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	2,899	7,322
Fair Value, Measurements, Recurring [Member] | Private label [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	8,428	11,116
Fair Value, Measurements, Recurring [Member] | Interest Rate Cap [Member] | Purchase [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	1	11
Fair Value, Measurements, Recurring [Member] | Interest Rate Cap [Member] | Written [Member]
Derivative Liabilities [Abstract]
Derivative Liabilities	1	11
Fair Value, Measurements, Recurring [Member] | Forward Contracts [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	102	0
Derivative Liabilities [Abstract]
Derivative Liabilities	280	138
Fair Value, Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	737	341
Fair Value, Measurements, Recurring [Member] | Forward loan sales commitments [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	20	20
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 1 [Member]
Assets Fair Value Disclosure [Abstract]
Equity Securities, FV-NI	1,474	1,428
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 1 [Member] | Interest Rate Swap [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	0	0
Derivative Liabilities [Abstract]
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 1 [Member] | Other Available For Sale Securities [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 1 [Member] | U S Treasury Securities [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	7,507	7,479
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 1 [Member] | Government Agencies Debt Securities [Member] | Noncallable [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 1 [Member] | Government Agencies Debt Securities [Member] | Call Option [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 1 [Member] | US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 1 [Member] | Private label [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 1 [Member] | Interest Rate Cap [Member] | Purchase [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 1 [Member] | Interest Rate Cap [Member] | Written [Member]
Derivative Liabilities [Abstract]
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 1 [Member] | Forward Contracts [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	0	0
Derivative Liabilities [Abstract]
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 1 [Member] | Interest Rate Lock Commitments [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 1 [Member] | Forward loan sales commitments [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 2 [Member]
Assets Fair Value Disclosure [Abstract]
Equity Securities, FV-NI	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 2 [Member] | Interest Rate Swap [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	1,622	0
Derivative Liabilities [Abstract]
Derivative Liabilities	1,639	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 2 [Member] | Other Available For Sale Securities [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 2 [Member] | U S Treasury Securities [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 2 [Member] | Government Agencies Debt Securities [Member] | Noncallable [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	173,371	146,777
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 2 [Member] | Government Agencies Debt Securities [Member] | Call Option [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	4,454,164	1,950,331
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	0	4,348
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 2 [Member] | Private label [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 2 [Member] | Interest Rate Cap [Member] | Purchase [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	1	11
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 2 [Member] | Interest Rate Cap [Member] | Written [Member]
Derivative Liabilities [Abstract]
Derivative Liabilities	1	11
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 2 [Member] | Forward Contracts [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	102	0
Derivative Liabilities [Abstract]
Derivative Liabilities	280	138
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 2 [Member] | Interest Rate Lock Commitments [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	737	341
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 2 [Member] | Forward loan sales commitments [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	20	20
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member]
Assets Fair Value Disclosure [Abstract]
Equity Securities, FV-NI	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Interest Rate Swap [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	0	0
Derivative Liabilities [Abstract]
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Other Available For Sale Securities [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	650	500
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | U S Treasury Securities [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Government Agencies Debt Securities [Member] | Noncallable [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Government Agencies Debt Securities [Member] | Call Option [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	2,899	2,974
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Private label [Member]
Assets Fair Value Disclosure [Abstract]
Available For Sale Securities	8,428	11,116
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Interest Rate Cap [Member] | Purchase [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Interest Rate Cap [Member] | Written [Member]
Derivative Liabilities [Abstract]
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Forward Contracts [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	0	0
Derivative Liabilities [Abstract]
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Interest Rate Lock Commitments [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 3 [Member] | Forward loan sales commitments [Member]
Assets Fair Value Disclosure [Abstract]
Derivative Assets	$ 0	$ 0