FAIR VALUE DISCLOSURES OF FINANCIAL ASSETS AND LIABILITIES - Schedule of Book Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Financial assets:
Investment securities, pledged for collateral	$ 3,502,159	$ 3,510,648
Stock in FHLB of Pittsburgh	20,149	11,805
Accrued interest receivable	79,512	84,671
Financial liabilities:
Deposits	17,226,218	17,029,808
Accrued interest payable	25,742	38,173
Level 1 | Book Value
Financial assets:
Cash, cash equivalents, and restricted cash	1,573,100	1,154,818
Level 1 | Fair Value
Financial assets:
Cash, cash equivalents, and restricted cash	1,573,100	1,154,818
Level 2 | Book Value
Financial assets:
Investment securities, pledged for collateral	3,502,159	3,510,648
Investment securities held-to-maturity, net	979,698	1,015,161
Loans, held for sale	63,047	49,699
Stock in FHLB of Pittsburgh	20,149	11,805
Accrued interest receivable	79,512	84,671
Financial liabilities:
Deposits	17,226,218	17,029,808
Borrowed funds	255,099	383,607
Accrued interest payable	25,742	38,173
Level 2 | Fair Value
Financial assets:
Investment securities, pledged for collateral	3,502,159	3,510,648
Investment securities held-to-maturity, net	886,182	895,511
Loans, held for sale	63,047	49,699
Stock in FHLB of Pittsburgh	20,149	11,805
Accrued interest receivable	79,512	84,671
Financial liabilities:
Deposits	17,215,671	17,016,839
Borrowed funds	259,338	379,154
Accrued interest payable	25,742	38,173
Level 3
Financial assets:
Other investments	15,489	15,516
Other assets	73	25
Level 3 | Book Value
Financial assets:
Other investments	17,715	18,184
Loans and leases, net	12,777,336	12,996,218
Financial liabilities:
Standby letters of credit	888	776
Level 3 | Fair Value
Financial assets:
Other investments	17,715	18,184
Loans and leases, net	12,967,725	13,100,492
Financial liabilities:
Standby letters of credit	888	776
Levels 2, 3 | Book Value
Financial assets:
Other assets	147,876	170,489
Financial liabilities:
Other liabilities	128,956	160,512
Levels 2, 3 | Fair Value
Financial assets:
Other assets	147,876	170,489
Financial liabilities:
Other liabilities	$ 128,956	$ 160,512