Quarterly report pursuant to Section 13 or 15(d)

Fair Value - Summary of the fair value and unpaid principal balance ("UPB") (Detail)

v3.21.2
Fair Value - Summary of the fair value and unpaid principal balance ("UPB") (Detail) - USD ($)
$ in Thousands
Jun. 30, 2021
Dec. 31, 2020
Estimated Fair Value    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Estimated Fair Value $ 10,316,027 $ 9,929,163
Unpaid Principal Balance    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Unpaid Principal Balance 9,406,924 9,045,104
Mortgage Loans Held For Investment Subject To Nonrecourse Debt [Member] | Estimated Fair Value | Reverse Mortgage Loans [Member]    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Estimated Fair Value 5,189,680 5,057,624
Mortgage Loans Held For Investment Subject To Nonrecourse Debt [Member] | Estimated Fair Value | Commercial Mortgage Loans [Member]    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Estimated Fair Value 234,941 338,543
Mortgage Loans Held For Investment Subject To Nonrecourse Debt [Member] | Unpaid Principal Balance | Reverse Mortgage Loans [Member]    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Unpaid Principal Balance 4,615,128 4,457,805
Mortgage Loans Held For Investment Subject To Nonrecourse Debt [Member] | Unpaid Principal Balance | Commercial Mortgage Loans [Member]    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Unpaid Principal Balance 229,858 333,344
Mortgage Loans Held For Investment [Member] | Estimated Fair Value | Reverse Mortgage Loans [Member]    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Estimated Fair Value 1,020,143 661,790
Mortgage Loans Held For Investment [Member] | Estimated Fair Value | Commercial Mortgage Loans [Member]    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Estimated Fair Value 204,947 69,031
Mortgage Loans Held For Investment [Member] | Unpaid Principal Balance | Reverse Mortgage Loans [Member]    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Unpaid Principal Balance 879,794 589,429
Mortgage Loans Held For Investment [Member] | Unpaid Principal Balance | Commercial Mortgage Loans [Member]    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Unpaid Principal Balance 202,195 69,127
Mortgage Loans Held For Sale [Member] | Estimated Fair Value | Commercial Mortgage Loans [Member]    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Estimated Fair Value 149,435 142,226
Mortgage Loans Held For Sale [Member] | Estimated Fair Value | Residential Mortgage Loans [Member]    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Estimated Fair Value 1,908,107 2,080,585
Mortgage Loans Held For Sale [Member] | Unpaid Principal Balance | Commercial Mortgage Loans [Member]    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Unpaid Principal Balance 144,789 140,693
Mortgage Loans Held For Sale [Member] | Unpaid Principal Balance | Residential Mortgage Loans [Member]    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Unpaid Principal Balance 1,858,087 2,000,795
HMBS Related Obligations [Member] | Estimated Fair Value    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Estimated Fair Value 10,168,224 9,788,668
HMBS Related Obligations [Member] | Unpaid Principal Balance    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Unpaid Principal Balance 9,406,924 9,045,104
Non Recourse Debt [Member] | Estimated Fair Value    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Estimated Fair Value 5,360,603 5,257,754
Non Recourse Debt [Member] | Unpaid Principal Balance    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Unpaid Principal Balance 5,276,781 5,155,017
Non Recourse MSR Financing Liability [Member] | Estimated Fair Value    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Estimated Fair Value 65,129 14,088
Non Recourse MSR Financing Liability [Member] | Unpaid Principal Balance    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Unpaid Principal Balance $ 65,129 $ 14,088