Derivative and Credit Risk Transfer Strip Assets and Liabilities - Summary of Derivative Assets, Financial Instruments and Collateral Held by Counterparty (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Offsetting Assets [Line Items]
Total derivative assets after netting	$ 90,753	$ 177,984
Financial instruments	0	0
Cash collateral received	0	0
Net amount	90,753	177,984
CRT Derivatives [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	24,305	16,160
Financial instruments	0	0
Cash collateral received	0	0
Net amount	24,305	16,160
Interest Rate Lock Commitments [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	2,587	7,596
Financial instruments	0	0
Cash collateral received	0	0
Net amount	2,587	7,596
Morgan Stanley & Co. LLC [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	47,095	79,825
Financial instruments	0	0
Cash collateral received	0	0
Net amount	47,095	79,825
RJ O'Brien & Associates, LLC [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	14,798	42,703
Financial instruments	0	0
Cash collateral received	0	0
Net amount	14,798	42,703
Wells Fargo Securities L L C
Offsetting Assets [Line Items]
Total derivative assets after netting	510	7,759
Financial instruments	0	0
Cash collateral received	0	0
Net amount	510	7,759
Athene Annuity And Life Assurance Company [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	475	94
Financial instruments	0	0
Cash collateral received	0	0
Net amount	475	94
Barclays Capital Inc. [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	295	0
Financial instruments	0	0
Cash collateral received	0	0
Net amount	295	0
Goldman Sachs & Co. LLC [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	240	18,701
Financial instruments	0	0
Cash collateral received	0	0
Net amount	240	18,701
J.P. Morgan Securities LLC [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	127	997
Financial instruments	0	0
Cash collateral received	0	0
Net amount	127	997
Bank of America, N.A. [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	0	3,418
Financial instruments	0	0
Cash collateral received	0	0
Net amount	0	3,418
Citigroup Global Markets Inc. [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	0	503
Financial instruments	0	0
Cash collateral received	0	0
Net amount	0	503
Other [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	321	228
Financial instruments	0	0
Cash collateral received	0	0
Net amount	$ 321	$ 228