FAIR VALUE DISCLOSURES OF FINANCIAL ASSETS AND LIABILITIES - Schedule of Book Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Financial assets:
Investment securities available-for-sale	$ 3,548,077	$ 3,510,648
Stock in FHLB of Pittsburgh	20,886	11,805
Accrued interest receivable	80,418	84,671
Financial liabilities:
Deposits	16,879,061	17,029,808
Accrued interest payable	35,947	38,173
Level 1 | Book Value
Financial assets:
Cash, cash equivalents, and restricted cash	1,017,294	1,154,818
Level 1 | Fair Value
Financial assets:
Cash, cash equivalents, and restricted cash	1,017,294	1,154,818
Level 2 | Book Value
Financial assets:
Investment securities available-for-sale	3,548,077	3,510,648
Investment securities held-to-maturity, net	1,006,410	1,015,161
Loans, held for sale	52,481	49,699
Stock in FHLB of Pittsburgh	20,886	11,805
Accrued interest receivable	80,418	84,671
Financial liabilities:
Deposits	16,879,061	17,029,808
Borrowed funds	318,092	383,607
Accrued interest payable	35,947	38,173
Level 2 | Fair Value
Financial assets:
Investment securities available-for-sale	3,548,077	3,510,648
Investment securities held-to-maturity, net	898,739	895,511
Loans, held for sale	52,481	49,699
Stock in FHLB of Pittsburgh	20,886	11,805
Accrued interest receivable	80,418	84,671
Financial liabilities:
Deposits	16,866,426	17,016,839
Borrowed funds	320,680	379,154
Accrued interest payable	35,947	38,173
Level 3
Financial assets:
Other investments	15,489	15,516
Other assets	33	25
Level 3 | Book Value
Financial assets:
Other investments	17,722	18,184
Loans and leases, net	12,922,842	12,996,218
Financial liabilities:
Standby letters of credit	699	776
Level 3 | Fair Value
Financial assets:
Other investments	17,722	18,184
Loans and leases, net	12,963,268	13,100,492
Financial liabilities:
Standby letters of credit	699	776
Levels 2, 3 | Book Value
Financial assets:
Other assets	149,781	170,489
Financial liabilities:
Other liabilities	137,122	160,512
Levels 2, 3 | Fair Value
Financial assets:
Other assets	149,781	170,489
Financial liabilities:
Other liabilities	$ 137,122	$ 160,512