Fair Values of Assets and Liabilities - Valuation Assumption Ranges for MSRs (Detail) - Mortgage Servicing Rights [Member]	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected prepayment	8.40%	7.80%
Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected prepayment	6.00%
Option adjusted spread	5.00%
Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected prepayment	20.00%
Option adjusted spread	11.00%
Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected prepayment	9.00%
Option adjusted spread	6.00%