v3.26.1
Assets Sold Under Agreements to Repurchase - Summary of Financial Information Relating to Assets Sold under Agreements to Repurchase (Detail) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Dec. 31, 2025
Assets Sold under Agreements to Repurchase [Line Items]      
Weighted average interest rate 4.64% 5.21%  
Average balance $ 7,812,433,000 $ 6,180,911,000  
Total interest expense 91,392,000 81,148,000  
Maximum daily amount outstanding 8,673,233,000 $ 7,068,600,000  
Assets Sold Under Agreements To Repurchase 7,304,211,000   $ 8,023,156,000
Assets sold under agreements to repurchase, At year end $ 7,300,692,000   $ 8,018,601,000
Weighted average interest rate 4.54%   4.71%
Available borrowing capacity, Committed $ 553,463,000   $ 595,085,000
Available borrowing capacity, Uncommitted 5,174,734,000   5,032,598,000
Available borrowing capacity 5,728,197,000   5,627,683,000
Margin deposits placed with counterparties included in Other assets, net 170,948,000   174,598,000
Assets Sold Under Agreements to Repurchase [Member]      
Assets Sold under Agreements to Repurchase [Line Items]      
Unamortized debt issuance costs (3,519,000)   (4,555,000)
Mortgage Backed Securities at Fair Value [Member]      
Assets Sold under Agreements to Repurchase [Line Items]      
Assets Sold under Agreements to Repurchase, Market Value 3,765,539,000   4,452,859,000
Loans Held for Sale at Fair Value [Member]      
Assets Sold under Agreements to Repurchase [Line Items]      
Assets Sold under Agreements to Repurchase, Market Value 2,328,824,000   2,676,700,000
Loans Held for Investment at Fair Value [Member]      
Assets Sold under Agreements to Repurchase [Line Items]      
Assets Sold under Agreements to Repurchase, Market Value 937,680,000   648,159,000
Servicing advances [Member]      
Assets Sold under Agreements to Repurchase [Line Items]      
Assets Sold under Agreements to Repurchase, Market Value 38,930,000   44,653,000
Derivative Assets [Member]      
Assets Sold under Agreements to Repurchase [Line Items]      
Assets Sold under Agreements to Repurchase, Market Value 9,169,000   12,622,000
Deposits Securing Credit Risk Transfer Arrangements [Member]      
Assets Sold under Agreements to Repurchase [Line Items]      
Assets Sold under Agreements to Repurchase, Market Value 153,742,000   176,694,000
Mortgage Service Rights at Fair Value [Member]      
Assets Sold under Agreements to Repurchase [Line Items]      
Assets Sold under Agreements to Repurchase, Market Value $ 1,745,231,000   $ 1,765,572,000