v3.26.1
Derivative and Credit Risk Transfer Strip Assets and Liabilities - Summary of Derivative Liabilities, Financial Liabilities and Collateral Pledged by Counterparty (Detail) - Unpaid Principal Balance Before Unamortized Debt Issuance Costs Adjustment [Member] - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet $ 8,401,658 $ 8,024,089
Gross amounts not offset in the consolidated balance sheet, Financial instruments (8,398,039) (8,023,156)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 3,619 933
Bank of America, N.A. [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 1,697,771 1,074,334
Gross amounts not offset in the consolidated balance sheet, Financial instruments (1,697,583) (1,074,334)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 188 0
Santander US Capital [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 1,327,157 952,951
Gross amounts not offset in the consolidated balance sheet, Financial instruments (1,327,157) (952,933)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 0 18
J.P. Morgan Securities LLC [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 1,007,543 1,536,038
Gross amounts not offset in the consolidated balance sheet, Financial instruments (1,007,388) (1,536,038)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 155 0
Wells Fargo Securities L L C | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 874,547 782,547
Gross amounts not offset in the consolidated balance sheet, Financial instruments (874,297) (782,547)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 250 0
Atlas Securitized Products, L.P. [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 707,813 1,216,779
Gross amounts not offset in the consolidated balance sheet, Financial instruments (707,813) (1,216,779)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 0 0
Barclays Capital Inc. [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 582,733 431,016
Gross amounts not offset in the consolidated balance sheet, Financial instruments (582,733) (431,016)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 0 0
Citigroup Global Markets Inc. [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 512,479 397,162
Gross amounts not offset in the consolidated balance sheet, Financial instruments (512,479) (397,162)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 0 0
RBC Capital Markets, L.P. [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 316,744 438,781
Gross amounts not offset in the consolidated balance sheet, Financial instruments (316,744) (438,781)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 0 0
Nomura Holdings America, Inc [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 271,832 231,308
Gross amounts not offset in the consolidated balance sheet, Financial instruments (271,832) (231,308)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 0 0
BNP Paribas [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 266,030 54,191
Gross amounts not offset in the consolidated balance sheet, Financial instruments (266,030) (54,191)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 0 0
Goldman Sachs & Co. LLC [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 255,065 151,274
Gross amounts not offset in the consolidated balance sheet, Financial instruments (254,477) (151,274)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 588 0
Bank of Montreal [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 209,904 160,388
Gross amounts not offset in the consolidated balance sheet, Financial instruments (209,834) (160,324)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 70 64
Daiwa Capital Markets [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 176,124 195,268
Gross amounts not offset in the consolidated balance sheet, Financial instruments (176,064) (195,268)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 60 0
Morgan Stanley & Co. LLC [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 124,569 319,500
Gross amounts not offset in the consolidated balance sheet, Financial instruments (123,904) (319,500)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 665 0
Mizuho Financial Group [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 69,704 81,701
Gross amounts not offset in the consolidated balance sheet, Financial instruments (69,704) (81,701)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 0 0
Other [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 1,643 851
Gross amounts not offset in the consolidated balance sheet, Financial instruments 0 0
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 1,643 851
PennyMac Financial Services, Inc. [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 1,234 2,257
Gross amounts not offset in the consolidated balance sheet, Financial instruments 0 0
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount $ 1,234 $ 2,257