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
Mar. 31, 2026
Dec. 31, 2025
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet $ 7,321,478 $ 8,024,089
Gross amounts not offset in the consolidated balance sheet, Financial instruments (7,304,211) (8,023,156)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 17,267 933
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 5,886 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 5,886 2,257
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 1,090,645 1,536,038
Gross amounts not offset in the consolidated balance sheet, Financial instruments (1,090,645) (1,536,038)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 0 0
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 1,012,219 1,074,334
Gross amounts not offset in the consolidated balance sheet, Financial instruments (1,012,219) (1,074,334)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 0 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 984,628 1,216,779
Gross amounts not offset in the consolidated balance sheet, Financial instruments (984,628) (1,216,779)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 0 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 973,270 952,951
Gross amounts not offset in the consolidated balance sheet, Financial instruments (973,270) (952,933)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 0 18
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 721,550 782,547
Gross amounts not offset in the consolidated balance sheet, Financial instruments (721,550) (782,547)
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 466,672 151,274
Gross amounts not offset in the consolidated balance sheet, Financial instruments (458,388) (151,274)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 8,284 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 381,942 438,781
Gross amounts not offset in the consolidated balance sheet, Financial instruments (381,942) (438,781)
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 332,396 431,016
Gross amounts not offset in the consolidated balance sheet, Financial instruments (331,360) (431,016)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 1,036 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 300,073 319,500
Gross amounts not offset in the consolidated balance sheet, Financial instruments (295,956) (319,500)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 4,117 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 272,553 231,308
Gross amounts not offset in the consolidated balance sheet, Financial instruments (272,553) (231,308)
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 273,174 397,162
Gross amounts not offset in the consolidated balance sheet, Financial instruments (272,324) (397,162)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 850 0
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 189,890 195,268
Gross amounts not offset in the consolidated balance sheet, Financial instruments (189,699) (195,268)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 191 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 145,344 160,388
Gross amounts not offset in the consolidated balance sheet, Financial instruments (144,928) (160,324)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 416 64
BNP Paribas [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 99,518 54,191
Gross amounts not offset in the consolidated balance sheet, Financial instruments (98,923) (54,191)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 595 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 76,637 81,701
Gross amounts not offset in the consolidated balance sheet, Financial instruments (75,826) (81,701)
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged 0 0
Net amount 811 0
Other [Member] | Security Sold Under Agreements to Repurchase [Member]    
Offsetting Liabilities [Line Items]    
Net amount of liabilities presented in the consolidated balance sheet 967 851
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 $ 967 $ 851