Transactions with Affiliates - Mortgage Loan Servicing (Details)		3 Months Ended		9 Months Ended
	Sep. 12, 2016 USD ($) item	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Summary of mortgage loan servicing fees earned
Loan servicing fees		$ 185,967,000	$ 147,182,000	$ 533,510,000	$ 421,536,000
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
Related party transaction, automatic renewal period	18 months
Minimum | Loan Servicing Agreement
Transactions with Affiliates
Servicing fees amount per month for current loans	$ 30
Maximum | Loan Servicing Agreement
Transactions with Affiliates
Servicing fees amount per month for severely delinquent loans	$ 85
PMT
Summary of mortgage loan servicing fees earned
Loan servicing fees		12,964,000	10,071,000	35,102,000	30,521,000
PMT | Loans acquired for sale at fair value
Summary of mortgage loan servicing fees earned
Loan servicing fees		507,000	316,000	1,131,000	739,000
PMT | Loans at fair value
Summary of mortgage loan servicing fees earned
Loan servicing fees		858,000	1,271,000	1,938,000	5,528,000
PMT | Mortgage servicing rights
Summary of mortgage loan servicing fees earned
Loan servicing fees		11,599,000	8,484,000	32,033,000	24,254,000
PMT | Other income.
Summary of mortgage loan servicing fees earned
Property management fees		$ 70,000	$ 122,000	$ 295,000	$ 333,000