Fair Values of Assets and Liabilities - Valuation Assumption Ranges for Derivative Commitments (Details)	Sep. 30, 2025
Minimum | Expected loan close rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative commitments measurement inputs	0.04
Minimum | Inherent MSR value (basis points per loan)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative commitments measurement inputs	0.0058
Maximum | Expected loan close rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative commitments measurement inputs	1
Maximum | Inherent MSR value (basis points per loan)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative commitments measurement inputs	0.0219
Weighted Average | Expected loan close rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative commitments measurement inputs	0.83
Weighted Average | Inherent MSR value (basis points per loan)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative commitments measurement inputs	0.0115