Loan Sales and Servicing Activities - Geographical Distribution of Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Loan Sales and Servicing Activities
Total loans serviced	$ 448,824,901	$ 426,750,830
California
Loan Sales and Servicing Activities
Total loans serviced	63,423,866	60,591,363
Florida
Loan Sales and Servicing Activities
Total loans serviced	37,181,908	35,360,190
Texas
Loan Sales and Servicing Activities
Total loans serviced	36,781,005	34,591,419
Virginia
Loan Sales and Servicing Activities
Total loans serviced	27,728,760	26,209,701
Maryland
Loan Sales and Servicing Activities
Total loans serviced	21,105,934	19,974,809
All other states
Loan Sales and Servicing Activities
Total loans serviced	$ 262,603,428	$ 250,023,348