Transactions with Affiliates - Financing Activities (Details) - PennyMac Mortgage Investment Trust - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 19, 2016
Financing activities:
Issuance pursuant to recapture agreement	$ 557,000	$ 2,093,000	$ 1,757,000
Repayments	134,624,000	32,377,000	40,316,000
Change in fair value	(1,037,000)	24,970,000	9,256,000
interest expense	1,280,000	8,418,000	10,291,000
Excess servicing spread financing at fair value payable to affiliate		131,750,000
2/1/13 Spread Acquisition Agreement
Financing activities:
Maximum ESS recapture obligation				$ 200,000
Excess servicing spread financing
Financing activities:
Balance at the beginning of the year	131,750,000	178,586,000	216,110,000
Issuance pursuant to recapture agreement	557,000	2,093,000	1,757,000
Repayments	(134,624,000)	(32,377,000)	(40,316,000)
Change in fair value	1,037,000	(24,970,000)	(9,256,000)
Balance at the end of the year		131,750,000	178,586,000
interest expense	1,280,000	8,418,000	10,291,000
Excess servicing spread recapture recognized	$ 614,000	$ 2,241,000	$ 1,726,000