Fair Values of Assets and Liabilities (Schedule of Valuation Techniques and Significant Unobservable Inputs Used to Measure Both Recurring and Non-Recurring) (Detail)	Jun. 30, 2022 USD ($) $ / shares year	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities, at fair value	$ 2,970,121,000		$ 2,327,793,000	$ 2,188,608,000
Loans held-for-investment	122,757,000			55,340,000
MSRs	212,664,000	$ 199,146,000	147,571,000	127,604,000	$ 124,316,000	$ 92,081,000
Individually assessed loans - foreclosure probable and collateral-dependent	85,557,000			113,854,000
Municipal securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities, at fair value	166,705,000		165,594,000	168,296,000
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Individually assessed loans - foreclosure probable and collateral-dependent	85,600,000
Measured at fair value on a recurring basis:
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage loans held-for-sale	513,232,000		817,912,000	984,994,000
Loans held-for-investment	122,757,000		38,598,000	55,340,000
MSRs	212,664,000		147,571,000	127,604,000
Derivative assets	183,925,000		165,008,000	212,380,000
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	166,705,000		165,594,000	168,296,000
Measured at fair value on a recurring basis: | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage loans held-for-sale	88,963,000		0	0
Loans held-for-investment	84,798,000		15,891,000	11,007,000
MSRs	212,664,000		147,571,000	127,604,000
Derivative assets	6,649,000		10,560,000	22,570,000
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	$ 113,485,000		$ 105,687,000	$ 117,606,000
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	0.0480
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	0.0480
MSRs, measurement input	0.07
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	0.0538
MSRs, measurement input	0.19
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	0.0480
Loans held-for-investment, measurement input	0.0486
MSRs, measurement input	0.0980
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	0.08
Loans held-for-investment, measurement input	0.08
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	0.0029
Loans held-for-investment, measurement input	0.0065
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	0.0682
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	0.0682
MSRs, measurement input	0.0682
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	11
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	2.5
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	1,000
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	318
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	0.22
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	0.849
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	$ 59,921,000
Other real estate owned	6,839,000
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	59,921,000
Other real estate owned	$ 6,839,000
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