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, 2024	Dec. 31, 2023
Financial assets:
Investment securities available-for-sale	$ 3,734,229	$ 3,846,537
Stock in FHLB of Pittsburgh	15,526	15,398
Accrued interest receivable	88,310	85,979
Financial liabilities:
Deposits	16,187,204	16,474,086
Accrued interest payable	37,911	46,684
Book Value | Level 1
Financial assets:
Cash, cash equivalents, and restricted cash	977,071	1,092,900
Book Value | Level 2
Financial assets:
Investment securities available-for-sale	3,734,229	3,846,537
Investment securities held-to-maturity, net	1,049,807	1,058,557
Loans, held for sale	26,858	29,268
Stock in FHLB of Pittsburgh	15,526	15,398
Accrued interest receivable	88,310	85,979
Financial liabilities:
Deposits	16,187,204	16,474,086
Borrowed funds	1,124,958	895,076
Accrued interest payable	37,911	46,684
Book Value | Level 3
Financial assets:
Other investments	17,051	17,434
Loans and leases, net	12,790,128	12,583,202
Financial liabilities:
Standby letters of credit	754	814
Book Value | Levels 2, 3
Financial assets:
Other assets	168,554	153,647
Financial liabilities:
Other liabilities	169,669	151,642
Fair Value | Level 1
Financial assets:
Cash, cash equivalents, and restricted cash	977,071	1,092,900
Fair Value | Level 2
Financial assets:
Investment securities available-for-sale	3,734,229	3,846,537
Investment securities held-to-maturity, net	949,727	985,931
Loans, held for sale	26,858	29,268
Stock in FHLB of Pittsburgh	15,526	15,398
Accrued interest receivable	88,310	85,979
Financial liabilities:
Deposits	16,160,641	16,449,198
Borrowed funds	1,134,269	912,760
Accrued interest payable	37,911	46,684
Fair Value | Level 3
Financial assets:
Other investments	17,051	17,434
Loans and leases, net	12,829,259	12,514,431
Financial liabilities:
Standby letters of credit	754	814
Fair Value | Levels 2, 3
Financial assets:
Other assets	168,554	153,647
Financial liabilities:
Other liabilities	$ 169,669	$ 151,642