Related Party Transactions - Mortgage Loan Servicing (Details)			3 Months Ended		9 Months Ended
	Jun. 30, 2020	Sep. 12, 2016 USD ($) item	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)
Loan Servicing Agreement
Transactions with Affiliates
Base servicing fees per month for REO		$ 75
Rental fee per month per REO		30
Renewal fee, per lease renewal, on REO property		$ 100
Property management fees on REOs, as a percent of gross rental income		9.00%
Base servicing fees per month for fixed-rate non-distressed loans subserviced		$ 7.50
Base servicing fees per month for adjustable rate non-distressed loans subserviced		8.50
Supplemental fee per month for each distressed whole loan		25
Activity-based fee, percent, due to a streamline modification		750
Activity-based fee, percent, due to a liquidation		1,750
Activity-based fee due to a deed-in-lieu of foreclosure		$ 500
Maximum number of liquidation, reperformance, or modification fees that can be earned during earnable period | item		1
Liquidation, reperformance, or modification fees earnable period		18 months
Minimum | Loan Servicing Agreement
Transactions with Affiliates
Servicing fees amount per month for current loans		$ 30
Additional servicing fee amount per month for delinquent loans		10
Maximum | Loan Servicing Agreement
Transactions with Affiliates
Servicing fees amount per month for severely delinquent loans		85
Additional servicing fee amount per month for delinquent loans		$ 55
PMT
Summary of mortgage loan servicing fees earned
Loan servicing fees			$ 18,752,000	$ 12,964,000	$ 48,806,000	$ 35,102,000
PMT | Loan Servicing Agreement
Summary of mortgage loan servicing fees earned
Related party transaction, renewal period	5 years
PMT | Loans acquired for sale at fair value
Summary of mortgage loan servicing fees earned
Loan servicing fees			452,000	507,000	1,595,000	1,131,000
PMT | Loans at fair value
Summary of mortgage loan servicing fees earned
Loan servicing fees			187,000	858,000	675,000	1,938,000
PMT | Mortgage servicing rights
Summary of mortgage loan servicing fees earned
Loan servicing fees			$ 18,113,000	11,599,000	$ 46,536,000	32,033,000
PMT | Other income.
Summary of mortgage loan servicing fees earned
Property management fees				$ 70,000		$ 295,000