Fair Value - Measurement Basis, Nonrecurring (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Total gains (losses) on assets measured at estimated fair values on a nonrecurring basis
Notes payable secured by mortgage servicing assets	$ 1,327,143		$ 1,327,143		$ 2,048,972
Unsecured Senior Notes	4,185,012		4,185,012		3,164,032
Term Notes and Term Loans
Total gains (losses) on assets measured at estimated fair values on a nonrecurring basis
Notes payable secured by mortgage servicing assets	1,227,143		1,227,143		1,724,120
Unsecured senior notes.
Total gains (losses) on assets measured at estimated fair values on a nonrecurring basis
Unsecured Senior Notes	4,185,012		4,185,012		3,164,032
Nonrecurring basis
Financial statement items measured at fair value on a nonrecurring basis
Real estate acquired in settlement of loans	6,125		6,125		5,238
Total gains (losses) on assets measured at estimated fair values on a nonrecurring basis
Real estate acquired in settlement of loans	(367)	$ (685)	(1,272)	$ (1,663)
Nonrecurring basis | Level 3
Financial statement items measured at fair value on a nonrecurring basis
Real estate acquired in settlement of loans	6,125		6,125		5,238
Total | Term Notes and Term Loans
Total gains (losses) on assets measured at estimated fair values on a nonrecurring basis
Notes payable secured by mortgage servicing assets	1,233,570		1,233,570		1,742,421
Total | Unsecured senior notes.
Total gains (losses) on assets measured at estimated fair values on a nonrecurring basis
Unsecured Senior Notes	$ 4,329,447		$ 4,329,447		$ 3,172,983