Transactions with Affiliates - Other Transactions, Reimbursement of Common Overhead Expenses (Details) - PMT - USD ($)		3 Months Ended		9 Months Ended
	Sep. 12, 2016	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
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		$ 3,605,000	$ 1,857,000	$ 7,416,000	$ 4,333,000
Payments and settlements during the period		68,191,000	21,650,000	111,411,000	45,265,000
Common overhead incurred
Reimbursement of common overhead and expenses incurred on behalf of affiliates
Reimbursement of common overhead and expenses incurred by the Company		1,543,000	1,210,000	4,055,000	3,387,000
Compensation
Reimbursement of common overhead and expenses incurred on behalf of affiliates
Reimbursement of common overhead and expenses incurred by the Company		120,000	120,000	360,000	360,000
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		$ 1,942,000	$ 527,000	$ 3,001,000	$ 586,000