Quarterly report pursuant to Section 13 or 15(d)

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

v3.22.1
Fair Value - Summary of the fair value and unpaid principal balance ("UPB") (Detail) - USD ($)
$ in Thousands
Mar. 31, 2022
Dec. 31, 2021
Estimated Fair Value    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Estimated Fair Value $ 10,672,152 $ 10,556,054
Unpaid Principal Balance 10,109,820 9,849,835
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 5,830,105 5,823,301
Unpaid Principal Balance 5,481,952 5,165,479
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 405,885 394,893
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 404,974 388,788
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 1,103,163 940,605
Unpaid Principal Balance 988,321 815,426
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 115,827 90,723
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 115,091 89,267
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 208,572 149,425
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 1,500,785 1,902,953
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 211,516 145,463
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 1,499,525 1,859,788
HMBS Related Obligations [Member] | Estimated Fair Value    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Estimated Fair Value 10,548,131 10,422,358
HMBS Related Obligations [Member] | Unpaid Principal Balance    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Unpaid Principal Balance 10,109,820 9,849,835
Non Recourse Debt [Member] | Estimated Fair Value    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Estimated Fair Value 6,032,157 5,857,069
Non Recourse Debt [Member] | Unpaid Principal Balance    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Unpaid Principal Balance 6,152,713 5,709,946
Nonrecourse Commercial Loan [Member] | Unpaid Principal Balance    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Estimated Fair Value 127,639 111,738
Unpaid Principal Balance 123,900 107,744
Nonrecourse Mortgage Service Rights [Member] | Unpaid Principal Balance    
Fair Value Summary Of The Fair Value And Unpaid Principal Balance Upb [Line Items]    
Estimated Fair Value 163,981 142,435
Unpaid Principal Balance $ 163,981 $ 142,435