Segments (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) segment	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Segments and Related Information
Number of segments | segment			3
Revenues:
Net gains on loans held for sale at fair value	$ 855,269	$ 235,732	$ 1,881,724	$ 468,041
Loan origination fees	75,572	49,434	192,091	110,288
Fulfillment fees from PennyMac Mortgage Investment Trust			149,594	102,313
Net loan servicing fees	132,807	66,229	412,952	205,934
Net interest income (expense):
Interest income	52,952	83,452	172,834	212,685
Interest expense, before non-segment activities	63,179	56,380	177,898	146,847
Net interest expense, before non-segment activities	(10,227)	27,072	(5,064)	65,838
Management fees	8,508	10,098	25,851	26,178
Other	3,224	2,633	6,303	8,437
Total net revenues, before non-segment activities	1,119,992	436,347	2,663,451	987,029
Expenses	391,701	270,150	1,040,068	660,951
Income before provision for income taxes	728,291	166,197	1,623,383	326,078
Assets:
Segment assets at period end	31,180,865		31,180,865		$ 10,204,017
PMT
Revenues:
Fulfillment fees from PennyMac Mortgage Investment Trust	54,839	45,149	149,594	102,313
Net interest income (expense):
Management fees	8,508	10,098	$ 25,851	26,178
Mortgage banking
Segments and Related Information
Number of segments | segment			2
Operating segment
Assets:
Segment assets at period end	31,180,865	9,303,199	$ 31,180,865	9,303,199
Operating segment | Investment management
Net interest income (expense):
Interest expense, before non-segment activities	4	21	18	39
Net interest expense, before non-segment activities	(4)	(21)	(18)	(39)
Management fees	8,508	10,098	25,851	26,178
Other	1,290	1,742	4,347	4,844
Total net revenues, before non-segment activities	9,794	11,819	30,180	30,983
Expenses	6,477	6,792	18,395	19,815
Income before provision for income taxes	3,317	5,027	11,785	11,168
Assets:
Segment assets at period end	17,917	19,281	17,917	19,281
Operating segment | Mortgage banking
Revenues:
Net gains on loans held for sale at fair value	855,269	235,732	1,881,724	468,041
Loan origination fees	75,572	49,434	192,091	110,288
Fulfillment fees from PennyMac Mortgage Investment Trust			149,594	102,313
Net loan servicing fees	132,807	66,229	412,952	205,934
Net interest income (expense):
Interest income	52,952	83,452	172,834	212,685
Interest expense, before non-segment activities	63,175	56,359	177,880	146,808
Net interest expense, before non-segment activities	(10,223)	27,093	(5,046)	65,877
Other	1,934	891	1,956	3,593
Total net revenues, before non-segment activities	1,110,198	424,528	2,633,271	956,046
Expenses	385,224	263,358	1,021,673	641,136
Income before provision for income taxes	724,974	161,170	1,611,598	314,910
Assets:
Segment assets at period end	31,162,948	9,283,918	31,162,948	9,283,918
Operating segment | Mortgage banking | PMT
Revenues:
Fulfillment fees from PennyMac Mortgage Investment Trust	54,839	45,149
Operating segment | Mortgage banking Production
Revenues:
Net gains on loans held for sale at fair value	700,830	216,132	1,637,193	407,713
Loan origination fees	75,572	49,434	192,091	110,288
Fulfillment fees from PennyMac Mortgage Investment Trust			149,594	102,313
Net interest income (expense):
Interest income	26,050	22,445	71,840	55,714
Interest expense, before non-segment activities	18,325	18,423	51,124	36,236
Net interest expense, before non-segment activities	7,725	4,022	20,716	19,478
Other	132	324	483	929
Total net revenues, before non-segment activities	839,098	315,061	2,000,077	640,721
Expenses	225,817	135,777	608,602	316,187
Income before provision for income taxes	613,281	179,284	1,391,475	324,534
Assets:
Segment assets at period end	7,319,838	4,850,741	7,319,838	4,850,741
Operating segment | Mortgage banking Production | PMT
Revenues:
Fulfillment fees from PennyMac Mortgage Investment Trust	54,839	45,149
Operating segment | Mortgage banking Servicing
Revenues:
Net gains on loans held for sale at fair value	154,439	19,600	244,531	60,328
Net loan servicing fees	132,807	66,229	412,952	205,934
Net interest income (expense):
Interest income	26,902	61,007	100,994	156,971
Interest expense, before non-segment activities	44,850	37,936	126,756	110,572
Net interest expense, before non-segment activities	(17,948)	23,071	(25,762)	46,399
Other	1,802	567	1,473	2,664
Total net revenues, before non-segment activities	271,100	109,467	633,194	315,325
Expenses	159,407	127,581	413,071	324,949
Income before provision for income taxes	111,693	(18,114)	220,123	(9,624)
Assets:
Segment assets at period end	$ 23,843,110	$ 4,433,177	$ 23,843,110	$ 4,433,177