Fair Value - Financial Statement Items Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Assets:
Short-term investment at fair value	$ 36,098	$ 6,873
Loans held for sale	4,149,726	9,742,483
Derivative assets:
Derivative asset, before netting	485,656	398,672
Netting	(321,496)	(64,977)
Total derivative assets	164,160	333,695
Investment in PennyMac Mortgage Investment Trust	884	1,300
Derivative liabilities:
Derivative liability, before netting	315,845	54,702
Netting	(190,358)	(32,096)
Net amounts of liabilities presented in the consolidated balance sheet	125,487	22,606
Mortgage servicing liabilities	2,214	2,816
Interest rate lock commitments
Derivative assets:
Total derivative assets	12,195	323,473
Forward contracts | Purchases
Derivative assets:
Derivative asset, before netting	5,042	20,485
Derivative liabilities:
Derivative liability, before netting	226,369	18,007
Forward contracts | Sales
Derivative assets:
Derivative asset, before netting	375,955	40,215
Derivative liabilities:
Derivative liability, before netting	8,819	35,415
MBS put options
Derivative assets:
Derivative asset, before netting	17,152	7,655
MBS call options
Derivative assets:
Derivative asset, before netting	55
Derivative liabilities:
Derivative liability, before netting	118
Call options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	4,680	2,078
Call options on Eurodollar futures | Sales
Derivative liabilities:
Derivative liability, before netting	375
Put options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	70,577	3,141
Put options on Eurodollar futures | Sales
Derivative liabilities:
Derivative liability, before netting	11,766
Level 3
Assets:
Loans held for sale	344,636	1,128,876
Recurring basis
Assets:
Short-term investment at fair value	36,098	6,873
Loans held for sale	4,149,726	9,742,483
Derivative assets:
Derivative asset, before netting	485,656	398,672
Netting	(321,496)	(64,977)
Total derivative assets	164,160	333,695
Mortgage servicing rights at fair value	5,661,672	3,878,078
Total assets	10,012,540	13,962,429
Derivative liabilities:
Derivative liability, before netting	315,845	54,702
Netting	(190,358)	(32,096)
Net amounts of liabilities presented in the consolidated balance sheet	125,487	22,606
Mortgage servicing liabilities	2,214	2,816
Total liabilities	127,701	25,422
Recurring basis | PennyMac Mortgage Investment Trust
Derivative assets:
Investment in PennyMac Mortgage Investment Trust	884	1,300
Recurring basis | Interest rate lock commitments
Derivative assets:
Derivative asset, before netting	12,195	323,473
Derivative liabilities:
Derivative liability, before netting	68,398	1,280
Recurring basis | Forward contracts | Purchases
Derivative assets:
Derivative asset, before netting	5,042	20,485
Derivative liabilities:
Derivative liability, before netting	226,369	18,007
Recurring basis | Forward contracts | Sales
Derivative assets:
Derivative asset, before netting	375,955	40,215
Derivative liabilities:
Derivative liability, before netting	8,819	35,415
Recurring basis | MBS put options
Derivative assets:
Derivative asset, before netting	17,152	7,655
Recurring basis | MBS call options
Derivative assets:
Derivative asset, before netting	55
Derivative liabilities:
Derivative liability, before netting	118
Recurring basis | Swaptions | Purchases
Derivative assets:
Derivative asset, before netting		1,625
Recurring basis | Call options on Eurodollar futures
Derivative liabilities:
Derivative liability, before netting	375
Recurring basis | Call options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	4,680	2,078
Recurring basis | Put options on Eurodollar futures
Derivative liabilities:
Derivative liability, before netting	11,766
Recurring basis | Put options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	70,577	3,141
Recurring basis | Level 1
Assets:
Short-term investment at fair value	36,098	6,873
Derivative assets:
Derivative asset, before netting	75,257	5,219
Total derivative assets	75,257	5,219
Total assets	112,239	13,392
Derivative liabilities:
Derivative liability, before netting	12,141
Net amounts of liabilities presented in the consolidated balance sheet	12,141
Total liabilities	12,141
Recurring basis | Level 1 | PennyMac Mortgage Investment Trust
Derivative assets:
Investment in PennyMac Mortgage Investment Trust	884	1,300
Recurring basis | Level 1 | Call options on Eurodollar futures
Derivative liabilities:
Derivative liability, before netting	375
Recurring basis | Level 1 | Call options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	4,680	2,078
Recurring basis | Level 1 | Put options on Eurodollar futures
Derivative liabilities:
Derivative liability, before netting	11,766
Recurring basis | Level 1 | Put options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	70,577	3,141
Recurring basis | Level 2
Assets:
Loans held for sale	3,805,090	8,613,607
Derivative assets:
Derivative asset, before netting	398,204	69,980
Total derivative assets	398,204	69,980
Total assets	4,203,294	8,683,587
Derivative liabilities:
Derivative liability, before netting	235,306	53,422
Net amounts of liabilities presented in the consolidated balance sheet	235,306	53,422
Total liabilities	235,306	53,422
Recurring basis | Level 2 | Forward contracts | Purchases
Derivative assets:
Derivative asset, before netting	5,042	20,485
Derivative liabilities:
Derivative liability, before netting	226,369	18,007
Recurring basis | Level 2 | Forward contracts | Sales
Derivative assets:
Derivative asset, before netting	375,955	40,215
Derivative liabilities:
Derivative liability, before netting	8,819	35,415
Recurring basis | Level 2 | MBS put options
Derivative assets:
Derivative asset, before netting	17,152	7,655
Recurring basis | Level 2 | MBS call options
Derivative assets:
Derivative asset, before netting	55
Derivative liabilities:
Derivative liability, before netting	118
Recurring basis | Level 2 | Swaptions | Purchases
Derivative assets:
Derivative asset, before netting		1,625
Recurring basis | Level 3
Assets:
Loans held for sale	344,636	1,128,876
Derivative assets:
Derivative asset, before netting	12,195	323,473
Total derivative assets	12,195	323,473
Mortgage servicing rights at fair value	5,661,672	3,878,078
Total assets	6,018,503	5,330,427
Derivative liabilities:
Derivative liability, before netting	68,398	1,280
Net amounts of liabilities presented in the consolidated balance sheet	68,398	1,280
Mortgage servicing liabilities	2,214	2,816
Total liabilities	70,612	4,096
Recurring basis | Level 3 | Interest rate lock commitments
Derivative assets:
Derivative asset, before netting	12,195	323,473
Derivative liabilities:
Derivative liability, before netting	$ 68,398	$ 1,280