Derivative and Credit Risk Transfer Strip Assets and Liabilities - Summary of Derivative Assets, Financial Instruments and Collateral Held by Counterparty (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Offsetting Assets [Line Items]
Total derivative assets after netting	$ 81,844	$ 177,984
Financial instruments	0	0
Cash collateral received	0	0
Net amount	81,844	177,984
CRT Derivatives [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	29,690	16,160
Financial instruments	0	0
Cash collateral received	0	0
Net amount	29,690	16,160
Interest Rate Lock Commitments [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	7,476	7,596
Financial instruments	0	0
Cash collateral received	0	0
Net amount	7,476	7,596
RJ O'Brien & Associates, LLC [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	14,797	42,703
Financial instruments	0	0
Cash collateral received	0	0
Net amount	14,797	42,703
Morgan Stanley & Co. LLC [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	10,699	79,825
Financial instruments	0	0
Cash collateral received	0	0
Net amount	10,699	79,825
Wells Fargo Securities L L C
Offsetting Assets [Line Items]
Total derivative assets after netting	7,666	7,759
Financial instruments	0	0
Cash collateral received	0	0
Net amount	7,666	7,759
Bank of America, N.A. [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	4,436	3,418
Financial instruments	0	0
Cash collateral received	0	0
Net amount	4,436	3,418
Goldman Sachs & Co. LLC [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	2,163	18,701
Financial instruments	0	0
Cash collateral received	0	0
Net amount	2,163	18,701
J.P. Morgan Securities LLC [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	1,307	997
Financial instruments	0	0
Cash collateral received	0	0
Net amount	1,307	997
Citigroup Global Markets Inc. [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	1,160	503
Financial instruments	0	0
Cash collateral received	0	0
Net amount	1,160	503
Other [Member]
Offsetting Assets [Line Items]
Total derivative assets after netting	2,450	322
Financial instruments	0	0
Cash collateral received	0	0
Net amount	$ 2,450	$ 322