FAIR VALUE DISCLOSURES OF FINANCIAL ASSETS AND LIABILITIES - Schedule of Book Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Financial assets:
Investment securities available-for-sale	$ 3,651,913	$ 3,846,537
Stock in FHLB of Pittsburgh	16,638	15,398
Accrued interest receivable	88,878	85,979
Financial liabilities:
Deposits	16,291,081	16,474,086
Accrued interest payable	56,684	46,684
Level 1 | Book Value
Financial assets:
Cash, cash equivalents, and restricted cash	1,021,716	1,092,900
Level 1 | Fair Value
Financial assets:
Cash, cash equivalents, and restricted cash	1,021,716	1,092,900
Level 2 | Book Value
Financial assets:
Investment securities available-for-sale	3,651,913	3,846,537
Investment securities held-to-maturity, net	1,038,854	1,058,557
Loans, held for sale	54,608	29,268
Stock in FHLB of Pittsburgh	16,638	15,398
Accrued interest receivable	88,878	85,979
Financial liabilities:
Deposits	16,291,081	16,474,086
Borrowed funds	1,142,255	895,076
Accrued interest payable	56,684	46,684
Level 2 | Fair Value
Financial assets:
Investment securities available-for-sale	3,651,913	3,846,537
Investment securities held-to-maturity, net	929,668	985,931
Loans, held for sale	54,608	29,268
Stock in FHLB of Pittsburgh	16,638	15,398
Accrued interest receivable	88,878	85,979
Financial liabilities:
Deposits	16,175,575	16,449,198
Borrowed funds	1,134,269	912,760
Accrued interest payable	56,684	46,684
Level 3 | Book Value
Financial assets:
Other investments	16,778	17,434
Loans and leases, net	12,945,948	12,583,202
Financial liabilities:
Standby letters of credit	754	814
Level 3 | Fair Value
Financial assets:
Other investments	16,778	17,434
Loans and leases, net	12,887,446	12,514,431
Financial liabilities:
Standby letters of credit	754	814
Levels 2, 3 | Book Value
Financial assets:
Other assets	175,078	153,647
Financial liabilities:
Other liabilities	169,775	151,642
Levels 2, 3 | Fair Value
Financial assets:
Other assets	175,078	153,647
Financial liabilities:
Other liabilities	$ 169,775	$ 151,642