Loan Sales and Servicing Activities - Geographical Distribution of Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Loan Sales and Servicing Activities
Total loans serviced	$ 348,475,008	$ 299,293,872
California
Loan Sales and Servicing Activities
Total loans serviced	55,400,197	51,377,441
Florida
Loan Sales and Servicing Activities
Total loans serviced	27,435,384	22,650,926
Texas
Loan Sales and Servicing Activities
Total loans serviced	26,509,926	23,648,042
Virginia
Loan Sales and Servicing Activities
Total loans serviced	21,056,414	19,011,950
Maryland
Loan Sales and Servicing Activities
Total loans serviced	15,968,754	13,774,011
All other states
Loan Sales and Servicing Activities
Total loans serviced	$ 202,104,333	$ 168,831,502