BORROWINGS - FHLB and FRB Advances (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
FHLB advances	$ 1,140,000
Amount
2025	0
2026	250,000
2027	710,000
2028	180,000
2029	0
Thereafter	0
FHLB advances	$ 1,140,000
Rate
2025	0
2026	4.38%
2027	4.03%
2028	4.43%
2029	0.00%
Thereafter	0.00%
Total maximum borrowing capacity with the FHLB	$ 3,876,351	$ 3,562,171
Total maximum borrowing capacity with the FRB	4,819,938	4,357,519
Qualifying loans and securities serving as collateral against FHLB and FRB	14,668,170	13,104,883
Qualifying Assets Pledged as Collateral
Rate
Qualifying loans and securities serving as collateral against FHLB and FRB	10,339,502	9,722,736
FHLB Advance Due March 2028
Debt Instrument [Line Items]
FHLB advances	750,000
Amount
FHLB advances	750,000
FHLB Advance Due December 2028
Debt Instrument [Line Items]
FHLB advances	390,000	390,000
Amount
FHLB advances	390,000	390,000
FHLB advances
Debt Instrument [Line Items]
Total long-term debt	$ 1,145,437	$ 1,028,352
Rate	4.17%	4.11%
Unamortized basis adjustments from interest rate swaps designated as fair value hedges of long-term advances from FHLB	$ 5,400	$ (1,600)