Segments (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) segment	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Segments and Related Information
Number of segments | segment	3
Revenues:
Net gains on loans held for sale at fair value	$ 754,341	$ 344,282
Loan origination fees	104,037	57,571
Net loan servicing fees	39,720	257,808
Net interest income (expense):
Interest income	82,081	72,564
Interest expense, before non-segment activities	107,713	61,512
Net interest expense, before non-segment activities	(25,632)	11,052
Management fees	8,449	9,055
Other	2,936	117
Total net revenues, before non-segment activities	944,686	721,825
Expenses	438,678	307,095
Income before provision for income taxes	506,008	414,730
Assets:
Segment assets at year end	31,297,980		$ 31,597,795
PMT
Revenues:
Fulfillment fees from PennyMac Mortgage Investment Trust	60,835	41,940
Net interest income (expense):
Management fees	$ 8,449	9,055
Mortgage banking
Segments and Related Information
Number of segments | segment	2
Operating segment
Assets:
Segment assets at year end	$ 31,297,980	10,891,133
Operating segment | Investment management
Net interest income (expense):
Interest expense, before non-segment activities	3	9
Net interest expense, before non-segment activities	(3)	(9)
Management fees	8,449	9,055
Other	1,142	807
Total net revenues, before non-segment activities	9,588	9,853
Expenses	8,219	6,096
Income before provision for income taxes	1,369	3,757
Assets:
Segment assets at year end	18,271	18,067
Operating segment | Mortgage banking
Revenues:
Net gains on loans held for sale at fair value	754,341	344,282
Loan origination fees	104,037	57,571
Net loan servicing fees	39,720	257,808
Net interest income (expense):
Interest income	82,081	72,564
Interest expense, before non-segment activities	107,710	61,503
Net interest expense, before non-segment activities	(25,629)	11,061
Other	1,794	(690)
Total net revenues, before non-segment activities	935,098	711,972
Expenses	430,459	300,999
Income before provision for income taxes	504,639	410,973
Assets:
Segment assets at year end	31,279,709	10,873,066
Operating segment | Mortgage banking | PMT
Revenues:
Fulfillment fees from PennyMac Mortgage Investment Trust	60,835	41,940
Operating segment | Mortgage banking Production
Revenues:
Net gains on loans held for sale at fair value	515,963	316,635
Loan origination fees	104,037	57,571
Net interest income (expense):
Interest income	29,531	26,585
Interest expense, before non-segment activities	38,072	20,157
Net interest expense, before non-segment activities	(8,541)	6,428
Other	597	(10)
Total net revenues, before non-segment activities	672,891	422,564
Expenses	309,996	182,433
Income before provision for income taxes	362,895	240,131
Assets:
Segment assets at year end	8,886,460	5,686,878
Operating segment | Mortgage banking Production | PMT
Revenues:
Fulfillment fees from PennyMac Mortgage Investment Trust	60,835	41,940
Operating segment | Mortgage banking Servicing
Revenues:
Net gains on loans held for sale at fair value	238,378	27,647
Net loan servicing fees	39,720	257,808
Net interest income (expense):
Interest income	52,550	45,979
Interest expense, before non-segment activities	69,638	41,346
Net interest expense, before non-segment activities	(17,088)	4,633
Other	1,197	(680)
Total net revenues, before non-segment activities	262,207	289,408
Expenses	120,463	118,566
Income before provision for income taxes	141,744	170,842
Assets:
Segment assets at year end	$ 22,393,249	$ 5,186,188