Related Party Transactions - Other Transactions, Reimbursement of Common Overhead Expenses (Details) - USD ($)			3 Months Ended		9 Months Ended
	Jul. 01, 2020	Sep. 12, 2016	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
PMT
Transactions with Affiliates
Expense reimbursement amount, per quarter, relating to personnel		$ 120,000
Reimbursement of common overhead and expenses incurred on behalf of affiliates
Reimbursement of common overhead and expenses incurred by the Company			$ 4,406,000	$ 3,605,000	$ 10,480,000	$ 7,416,000
Payments and settlements during the period			58,479,000	68,191,000	228,514,000	111,411,000
PMT | Common overhead incurred
Reimbursement of common overhead and expenses incurred on behalf of affiliates
Reimbursement of common overhead and expenses incurred by the Company			1,389,000	1,543,000	4,514,000	4,055,000
PMT | Compensation
Reimbursement of common overhead and expenses incurred on behalf of affiliates
Reimbursement of common overhead and expenses incurred by the Company			165,000	120,000	405,000	360,000
PMT | Expenses incurred by related party (reporting entity), net
Reimbursement of common overhead and expenses incurred on behalf of affiliates
Reimbursement of common overhead and expenses incurred by the Company			$ 2,852,000	$ 1,942,000	$ 5,561,000	$ 3,001,000
PCM
Transactions with Affiliates
Expense reimbursement amount, per quarter, relating to personnel	$ 165,000	$ 120,000
Related party transaction, renewal period	5 years