Segments (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segments and Related Information
Number of segments | item									3
Revenues:
Net gains on loans held for sale at fair value	$ 257,487	$ 235,732	$ 147,533	$ 84,776	$ 59,748	$ 56,914	$ 60,946	$ 71,414	$ 725,528	$ 249,022	$ 391,804
Loan origination fees	63,868	49,434	36,924	23,930	26,165	26,485	24,428	24,563	174,156	101,641	119,202
Net loan servicing fees	87,731	66,229	59,134	80,571	105,212	109,703	113,689	116,789	293,665	445,393	306,059
Net interest income (expense):
Interest income									288,700	216,416	143,179
Interest expense, before non-segment activities									211,979	144,597	144,520
Net interest expense, before non-segment activities									76,721	71,819	(1,341)
Management fees									36,492	24,469	23,585
Carried interest from Investment Funds										(365)	(1,040)
Other									10,232	10,174	3,895
Total net revenues, before non-segment activities									1,477,404	983,503	922,523
Expenses	287,009	270,150	203,387	187,414	192,895	189,232	169,600	165,205	947,960	716,932	619,554
Income (loss) before provision for income taxes and non-segment activities										266,571	302,969
Non-segment activities										1,126	32,940
Income before provision for income taxes	203,366	166,197	99,590	60,291	58,306	61,697	74,698	72,996	529,444	267,697	335,909
Assets:
Segment assets at year end	10,204,017	9,303,199	8,398,376	7,819,000	7,478,573	6,992,530	6,841,706	6,902,891	10,204,017	7,478,573
PMT
Revenues:
Fulfillment fees from PennyMac Mortgage Investment Trust	58,297	$ 45,149	$ 29,590	$ 27,574	28,591	$ 26,256	$ 14,559	$ 11,944	160,610	81,350	80,359
Net interest income (expense):
Management fees									$ 36,492	24,465	22,584
Investment Funds
Net interest income (expense):
Management fees										4	1,001
Carried interest from Investment Funds										(365)	(1,040)
Mortgage banking
Segments and Related Information
Number of segments | item									2
Operating segment
Assets:
Segment assets at year end	10,204,017				7,478,498				$ 10,204,017	7,478,498	7,365,488
Non-segment activities change in federal tax rate under the Tax Act											32,000
Working capital					75,000,000					75,000,000	2,600
Operating segment | Investment management
Net interest income (expense):
Interest income										16
Interest expense, before non-segment activities									56	49	49
Net interest expense, before non-segment activities									(56)	(33)	(49)
Management fees									36,492	24,469	23,585
Other									6,300	5,516	183
Total net revenues, before non-segment activities									42,736	29,587	22,679
Expenses									26,375	22,584	16,890
Income (loss) before provision for income taxes and non-segment activities										7,003	5,789
Income before provision for income taxes									16,361	7,003	5,789
Assets:
Segment assets at year end	19,996				11,681				19,996	11,681	19,880
Operating segment | Investment management | Investment Funds
Net interest income (expense):
Carried interest from Investment Funds										(365)	(1,040)
Operating segment | Mortgage banking
Revenues:
Net gains on loans held for sale at fair value									725,528	249,022	391,804
Loan origination fees									174,156	101,641	119,202
Net loan servicing fees									293,665	445,393	306,059
Net interest income (expense):
Interest income									288,700	216,400	143,179
Interest expense, before non-segment activities									211,923	144,548	144,471
Net interest expense, before non-segment activities									76,777	71,852	(1,292)
Other									3,932	4,658	3,712
Total net revenues, before non-segment activities									1,434,668	953,916	899,844
Expenses									921,585	694,348	602,664
Income (loss) before provision for income taxes and non-segment activities										259,568	297,180
Income before provision for income taxes									513,083	259,568	297,180
Assets:
Segment assets at year end	10,184,021				7,466,817				10,184,021	7,466,817	7,345,608
Operating segment | Mortgage banking | PMT
Revenues:
Fulfillment fees from PennyMac Mortgage Investment Trust									160,610	81,350	80,359
Operating segment | Mortgage banking Production
Revenues:
Net gains on loans held for sale at fair value									635,464	141,959	286,242
Loan origination fees									174,156	101,641	119,202
Net interest income (expense):
Interest income									82,338	66,408	61,195
Interest expense, before non-segment activities									59,973	7,371	35,359
Net interest expense, before non-segment activities									22,365	59,037	25,836
Other									1,289	2,008	2,002
Total net revenues, before non-segment activities									993,884	385,995	513,641
Expenses									466,050	298,729	275,133
Income (loss) before provision for income taxes and non-segment activities										87,266	238,508
Income before provision for income taxes									527,834	87,266	238,508
Assets:
Segment assets at year end	4,836,472				2,434,897				4,836,472	2,434,897	2,459,014
Operating segment | Mortgage banking Production | PMT
Revenues:
Fulfillment fees from PennyMac Mortgage Investment Trust									160,610	81,350	80,359
Operating segment | Mortgage banking Servicing
Revenues:
Net gains on loans held for sale at fair value									90,064	107,063	105,562
Net loan servicing fees									293,665	445,393	306,059
Net interest income (expense):
Interest income									206,362	149,992	81,984
Interest expense, before non-segment activities									151,950	137,177	109,112
Net interest expense, before non-segment activities									54,412	12,815	(27,128)
Other									2,643	2,650	1,710
Total net revenues, before non-segment activities									440,784	567,921	386,203
Expenses									455,535	395,619	327,531
Income (loss) before provision for income taxes and non-segment activities										172,302	58,672
Income before provision for income taxes									(14,751)	172,302	58,672
Assets:
Segment assets at year end	$ 5,347,549				$ 5,031,920				$ 5,347,549	$ 5,031,920	$ 4,886,594