Fair Values of Assets and Liabilities (Schedule of Valuation Techniques and Significant Unobservable Inputs Used to Measure Both Recurring and Non-Recurring) (Detail)	Sep. 30, 2022 USD ($) $ / shares year	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities, at fair value	$ 2,923,653,000		$ 2,327,793,000	$ 2,373,478,000
Loans held-for-investment	156,893,000			30,979,000
MSRs	229,671,000	$ 212,664,000	147,571,000	133,552,000	$ 127,604,000	$ 92,081,000
Individually assessed loans - foreclosure probable and collateral-dependent	105,365,000			109,011,000
Municipal securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities, at fair value	174,001,000		165,594,000	174,600,000
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Individually assessed loans - foreclosure probable and collateral-dependent	105,400,000
Measured at fair value on a recurring basis:
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage loans held-for-sale	376,160,000		817,912,000	925,312,000
Loans held-for-investment	156,893,000		38,598,000	30,979,000
MSRs	229,671,000		147,571,000	133,552,000
Derivative assets	313,480,000		165,008,000	191,612,000
Measured at fair value on a recurring basis: | Municipal securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities, at fair value	174,001,000		165,594,000	174,600,000
Measured at fair value on a recurring basis: | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage loans held-for-sale	48,420,000		0	0
Loans held-for-investment	98,567,000		15,891,000	12,132,000
MSRs	229,671,000		147,571,000	133,552,000
Derivative assets	141,000		10,560,000	14,612,000
Measured at fair value on a recurring basis: | Level 3 | Municipal securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities, at fair value	$ 122,432,000		$ 105,687,000	$ 117,724,000
Measured at fair value on a recurring basis: | Discount rate | Level 3 | Discounted cash flows
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage loans held-for-sale, measurement input	0.0619
Measured at fair value on a recurring basis: | Discount rate | Level 3 | Discounted cash flows | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held-for-investment, measurement input	0.0600
MSRs, measurement input	0.08
Measured at fair value on a recurring basis: | Discount rate | Level 3 | Discounted cash flows | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held-for-investment, measurement input	0.0650
MSRs, measurement input	0.20
Measured at fair value on a recurring basis: | Discount rate | Level 3 | Discounted cash flows | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage loans held-for-sale, measurement input	0.0619
Loans held-for-investment, measurement input	0.0621
MSRs, measurement input	0.1029
Measured at fair value on a recurring basis: | Credit discount | Level 3 | Discounted cash flows | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage loans held-for-sale, measurement input	0
Loans held-for-investment, measurement input	0
Measured at fair value on a recurring basis: | Credit discount | Level 3 | Discounted cash flows | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage loans held-for-sale, measurement input	0.14
Loans held-for-investment, measurement input	0.35
Measured at fair value on a recurring basis: | Credit discount | Level 3 | Discounted cash flows | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage loans held-for-sale, measurement input	0.0023
Loans held-for-investment, measurement input	0.0061
Measured at fair value on a recurring basis: | Constant prepayment rate (CPR) - current loans | Level 3 | Discounted cash flows
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held-for-investment, measurement input	0.0649
Measured at fair value on a recurring basis: | Constant prepayment rate (CPR) - current loans | Level 3 | Discounted cash flows | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
MSRs, measurement input	0
Measured at fair value on a recurring basis: | Constant prepayment rate (CPR) - current loans | Level 3 | Discounted cash flows | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
MSRs, measurement input	0.90
Measured at fair value on a recurring basis: | Constant prepayment rate (CPR) - current loans | Level 3 | Discounted cash flows | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held-for-investment, measurement input	0.0649
MSRs, measurement input	0.0649
Measured at fair value on a recurring basis: | Average life - delinquent loans (in years) | Level 3 | Discounted cash flows | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held-for-investment, measurement input | year	1
Measured at fair value on a recurring basis: | Average life - delinquent loans (in years) | Level 3 | Discounted cash flows | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held-for-investment, measurement input | year	13
Measured at fair value on a recurring basis: | Average life - delinquent loans (in years) | Level 3 | Discounted cash flows | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held-for-investment, measurement input | year	5.5
Measured at fair value on a recurring basis: | Cost of servicing | Level 3 | Discounted cash flows | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
MSRs, measurement input | $ / shares	70
Measured at fair value on a recurring basis: | Cost of servicing | Level 3 | Discounted cash flows | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
MSRs, measurement input | $ / shares	200
Measured at fair value on a recurring basis: | Cost of servicing | Level 3 | Discounted cash flows | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
MSRs, measurement input	75
Measured at fair value on a recurring basis: | Cost of servicing - delinquent | Level 3 | Discounted cash flows | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
MSRs, measurement input | $ / shares	200
Measured at fair value on a recurring basis: | Cost of servicing - delinquent | Level 3 | Discounted cash flows | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
MSRs, measurement input | $ / shares	1,250
Measured at fair value on a recurring basis: | Cost of servicing - delinquent | Level 3 | Discounted cash flows | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
MSRs, measurement input	371
Measured at fair value on a recurring basis: | Pull-through rate | Level 3 | Discounted cash flows | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives, measurement input	0.02
Measured at fair value on a recurring basis: | Pull-through rate | Level 3 | Discounted cash flows | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives, measurement input	1
Measured at fair value on a recurring basis: | Pull-through rate | Level 3 | Discounted cash flows | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives, measurement input	0.8548
Measured at fair value on a non-recurring basis:
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Individually assessed loans - foreclosure probable and collateral-dependent	$ 81,889,000
Other real estate owned	6,687,000
Measured at fair value on a non-recurring basis: | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Individually assessed loans - foreclosure probable and collateral-dependent	81,889,000
Other real estate owned	$ 6,687,000
Measured at fair value on a non-recurring basis: | Appraisal adjustment - cost of sale | Level 3 | Appraisal value
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Individually assessed loans— foreclosure probable and collateral-dependent, measurement input	0.10
Other real estate owned, measurement input	0.10
Measured at fair value on a non-recurring basis: | Appraisal adjustment - cost of sale | Level 3 | Appraisal value | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Individually assessed loans— foreclosure probable and collateral-dependent, measurement input	0.1000
Other real estate owned, measurement input	0.1000