Fair Value - Level 3 Input Roll Forward, Recurring Basis (Details) - Recurring basis - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the quarter	$ 10,184,315	$ 8,391,906	$ 9,212,146	$ 7,667,505
Purchases and issuances, net	1,922,823	1,259,911	5,175,280	3,348,364
Capitalization of interest and advances	29,575	15,282	67,522	40,618
Sales and repayments	(804,377)	(384,101)	(1,856,145)	(1,125,088)
Mortgage servicing rights resulting from loan sales	700,326	578,982	2,165,213	1,532,709
Changes in fair value included in income arising from:
Changes in instrument specific credit risk	40,810	36,968	108,439	82,121
Other factors	(242,964)	(477,547)	(723,301)	(577,586)
Total changes in fair value included in income	(202,154)	(440,579)	(614,862)	(495,465)
Transfers from Level 3 to Level 2	1,158,543	(648,238)	(3,046,586)	(1,915,061)
To real estate acquired in settlement of loans	(183)		(183)
Transfers to loans held for sale	(443,349)	(346,862)	(873,952)	(627,281)
Exchange of mortgage servicing spread for interest only stripped mortgage-backed securities		(121,520)		(121,520)
Balance at the end of the quarter	10,228,433	8,304,781	10,228,433	8,304,781
Changes in fair value recognized during the period relating to assets still held at the end of the quarter	$ (238,212)	$ (467,483)	$ (912,510)	$ (605,081)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Servicing Asset at Fair Value, Period Increase (Decrease)	Servicing Asset at Fair Value, Period Increase (Decrease)	Servicing Asset at Fair Value, Period Increase (Decrease)	Servicing Asset at Fair Value, Period Increase (Decrease)
Roll forward of liabilities measured using Level 3 inputs on a recurring basis
Balance at the beginning of the quarter	$ 1,643	$ 1,708	$ 1,683	$ 1,805
Changes in fair value included in income	(50)	10	(90)	(87)
Balance at the end of the quarter	1,593	1,718	1,593	1,718
Changes in fair value recognized during the period relating to liability still outstanding at the end of the quarter	(50)	10	(90)	(87)
Mortgage loans held for sale
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the quarter	510,913	400,076	434,053	478,564
Purchases and issuances, net	1,643,869	1,013,520	4,540,796	2,873,461
Capitalization of interest and advances	29,575	15,282	67,522	40,618
Sales and repayments	(618,968)	(384,101)	(1,670,736)	(1,125,088)
Changes in fair value included in income arising from:
Changes in instrument specific credit risk	40,810	36,968	108,439	82,121
Other factors	5,428	367	19,596	(741)
Total changes in fair value included in income	46,238	37,335	128,035	81,380
Transfers from Level 3 to Level 2	1,158,543	(648,238)	(3,046,586)	(1,915,061)
To real estate acquired in settlement of loans	(183)		(183)
Balance at the end of the quarter	452,901	433,874	452,901	433,874
Changes in fair value recognized during the period relating to assets still held at the end of the quarter	26,561	29,833	27,716	28,536
Interest rate lock commitments
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the quarter	148,638	68,752	34,009	89,593
Purchases and issuances, net	292,487	246,391	656,169	474,903
Changes in fair value included in income arising from:
Other factors	155,122	150,334	350,703	181,400
Total changes in fair value included in income	155,122	150,334	350,703	181,400
Transfers to loans held for sale	(469,168)	(346,862)	(913,802)	(627,281)
Balance at the end of the quarter	127,079	118,615	127,079	118,615
Changes in fair value recognized during the period relating to assets still held at the end of the quarter	127,079	118,615	127,079	118,615
Interest rate lock commitments | PennyMac Mortgage Investment Trust
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the quarter	(6,485)		(444)
Purchases and issuances, net	(13,533)		(21,685)
Changes in fair value included in income arising from:
Other factors	(11,290)		(23,210)
Total changes in fair value included in income	(11,290)		(23,210)
Transfers to loans held for sale	25,819		39,850
Balance at the end of the quarter	(5,489)		(5,489)
Changes in fair value recognized during the period relating to assets still held at the end of the quarter	(5,489)		(5,489)
Mortgage servicing rights
Roll forward of assets measured using Level 3 inputs on a recurring basis
Balance at the beginning of the quarter	9,531,249	7,923,078	8,744,528	7,099,348
Sales and repayments	(185,409)		(185,409)
Mortgage servicing rights resulting from loan sales	700,326	578,982	2,165,213	1,532,709
Changes in fair value included in income arising from:
Other factors	(392,224)	(628,248)	(1,070,390)	(758,245)
Total changes in fair value included in income	(392,224)	(628,248)	(1,070,390)	(758,245)
Exchange of mortgage servicing spread for interest only stripped mortgage-backed securities		(121,520)		(121,520)
Balance at the end of the quarter	9,653,942	7,752,292	9,653,942	7,752,292
Changes in fair value recognized during the period relating to assets still held at the end of the quarter	$ (386,363)	$ (615,931)	$ (1,061,816)	$ (752,232)