Transactions with Affiliates - Financing Activities (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Feb. 01, 2013
Financing activities:
Issuance pursuant to recapture agreement			$ 1,983,000	$ 4,160,000
Interest expense from excess servicing spread financing			11,584,000	13,011,000
PMT
Financing activities:
Changes in fair value included in income	$ (1,109,000)	$ 4,828,000	(9,026,000)	14,757,000
Excess servicing spread financing at fair value payable to affiliate	223,275,000		223,275,000		$ 236,534,000
PMT | 2/1/13 Spread Acquisition Agreement
Financing activities:
Maximum ESS recapture obligation						$ 200,000
Excess servicing spread financing
Financing activities:
Changes in fair value included in income	1,109,000	(4,828,000)	9,026,000	(14,757,000)
Excess servicing spread financing | PMT
Financing activities:
Issuance pursuant to recapture agreement	499,000	1,207,000	1,983,000	4,160,000
Repayments	11,543,000	13,410,000	35,852,000	42,320,000
Changes in fair value included in income	1,109,000	(4,828,000)	9,026,000	(14,757,000)
Interest expense from excess servicing spread financing	3,740,000	3,998,000	11,584,000	13,011,000
Excess servicing spread recapture recognized	597,000	$ 1,163,000	1,951,000	$ 3,837,000
Excess servicing spread financing at fair value payable to affiliate	$ 223,275,000		$ 223,275,000		$ 236,534,000