FAIR VALUE DISCLOSURES OF FINANCIAL ASSETS AND LIABILITIES - Book Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Financial assets:
Investment securities available-for-sale	$ 4,153,615	$ 5,205,311
Stock in FHLB of Pittsburgh	24,117	6,073
Accrued interest receivable	63,393	41,596
Financial liabilities:
Deposits	16,725,208	13,240,062
Accrued interest payable	5,568	736
Book Value | Level 1
Financial assets:
Cash, cash equivalents, and restricted cash	1,031,391	1,532,939
Book Value | Levels 2, 3
Financial liabilities:
Other liabilities	179,435	23,291
Book Value | Level 2
Financial assets:
Investment securities available-for-sale	4,153,615	5,205,311
Investment securities held-to-maturity, net	1,121,895	90,642
Loans, held for sale	61,671	113,349
Stock in FHLB of Pittsburgh	24,117	6,073
Accrued interest receivable	63,393	41,596
Other assets	163,229	5,153
Financial liabilities:
Deposits	16,725,208	13,240,062
Borrowed funds	374,367	239,477
Accrued interest payable	5,568	736
Book Value | Level 3
Financial assets:
Other investments	25,122	10,518
Loans and leases, net	11,559,195	7,791,482
Financial liabilities:
Standby letters of credit	596	674
Fair Value | Level 1
Financial assets:
Cash, cash equivalents, and restricted cash	1,031,391	1,532,939
Fair Value | Levels 2, 3
Financial liabilities:
Other liabilities	179,435	23,291
Fair Value | Level 2
Financial assets:
Investment securities available-for-sale	4,153,615	5,205,311
Investment securities held-to-maturity, net	1,041,163	94,131
Loans, held for sale	61,671	113,349
Stock in FHLB of Pittsburgh	24,117	6,073
Accrued interest receivable	63,393	41,596
Other assets	163,229	5,153
Financial liabilities:
Deposits	16,677,292	13,236,816
Borrowed funds	347,388	225,119
Accrued interest payable	5,568	736
Fair Value | Level 3
Financial assets:
Other investments	25,122	10,518
Loans and leases, net	11,471,216	7,723,867
Financial liabilities:
Standby letters of credit	$ 596	$ 674