Fair Value - Measurement Basis, Nonrecurring (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 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	$ 1,724,608		$ 2,048,972
Unsecured Senior Notes	3,998,702		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	1,724,608		1,724,120
Unsecured senior notes.
Total gains (losses) on assets measured at estimated fair values on a nonrecurring basis
Unsecured Senior Notes	3,998,702		3,164,032
Nonrecurring basis
Financial statement items measured at fair value on a nonrecurring basis
Real estate acquired in settlement of loans	5,365		5,238
Total gains (losses) on assets measured at estimated fair values on a nonrecurring basis
Real estate acquired in settlement of loans	(562)	$ (1,210)
Nonrecurring basis | Level 3
Financial statement items measured at fair value on a nonrecurring basis
Real estate acquired in settlement of loans	5,365		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	1,742,152		1,742,421
Total | Unsecured senior notes.
Total gains (losses) on assets measured at estimated fair values on a nonrecurring basis
Unsecured Senior Notes	$ 4,042,296		$ 3,172,983