Fair Value - Financial Statement Items Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Assets:
Short-term investment at fair value	$ 69	$ 10,268
Principal-only stripped mortgage-backed securities at fair value pledged to creditors	524,576
Loans held for sale	5,200,350	4,420,691
Derivative assets:
Derivative asset, before netting	145,678	258,809
Netting	(36,691)	(79,730)
Total derivative assets	108,987	179,079
Investment in PennyMac Mortgage Investment Trust	1,101	1,121
Derivative liabilities:
Derivative liability, before netting	46,435	101,866
Netting	(5,651)	(48,591)
Net amounts of liabilities presented in the consolidated balance sheet	40,784	53,275
Mortgage servicing liabilities	1,732	1,805
Interest rate lock commitments
Derivative assets:
Total derivative assets	74,545	90,313
Forward contracts | Purchases
Derivative assets:
Derivative asset, before netting	21,887	78,448
Derivative liabilities:
Derivative liability, before netting	6,049	5,141
Forward contracts | Sales
Derivative assets:
Derivative asset, before netting	18,622	6,151
Derivative liabilities:
Derivative liability, before netting	35,649	92,796
MBS put options
Derivative assets:
Derivative asset, before netting	1,970	413
MBS call options
Derivative assets:
Derivative asset, before netting		6,265
Call options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	3,301	66,176
Derivative liabilities:
Derivative liability, before netting		3,209
Put options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	25,353	11,043
Principal-Only-Strip MBS
Assets:
Principal-only stripped mortgage-backed securities at fair value pledged to creditors	524,576
Recurring basis
Assets:
Short-term investment at fair value	69	10,268
Principal-only stripped mortgage-backed securities at fair value pledged to creditors	524,576
Loans held for sale	5,200,350	4,420,691
Derivative assets:
Derivative asset, before netting	145,678	258,809
Netting	(36,691)	(79,730)
Total derivative assets	108,987	179,079
Mortgage servicing rights	7,483,210	7,099,348
Total assets	13,318,293	11,710,507
Derivative liabilities:
Derivative liability, before netting	46,435	101,866
Netting	(5,651)	(48,591)
Net amounts of liabilities presented in the consolidated balance sheet	40,784	53,275
Mortgage servicing liabilities	1,732	1,805
Total liabilities	42,516	55,080
Recurring basis | Related Party | PennyMac Mortgage Investment Trust
Derivative assets:
Investment in PennyMac Mortgage Investment Trust	1,101	1,121
Recurring basis | Interest rate lock commitments
Derivative assets:
Derivative asset, before netting	74,545	90,313
Derivative liabilities:
Derivative liability, before netting	4,737	720
Recurring basis | Forward contracts | Purchases
Derivative assets:
Derivative asset, before netting	21,887	78,448
Derivative liabilities:
Derivative liability, before netting	6,049	5,141
Recurring basis | Forward contracts | Sales
Derivative assets:
Derivative asset, before netting	18,622	6,151
Derivative liabilities:
Derivative liability, before netting	35,649	92,796
Recurring basis | MBS put options
Derivative assets:
Derivative asset, before netting	1,970	413
Recurring basis | MBS call options
Derivative assets:
Derivative asset, before netting		6,265
Recurring basis | Call options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	3,301	66,176
Recurring basis | Call options on Eurodollar futures | Sales
Derivative liabilities:
Derivative liability, before netting		3,209
Recurring basis | Put options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	25,353	11,043
Recurring basis | Level 1
Assets:
Short-term investment at fair value	69	10,268
Derivative assets:
Derivative asset, before netting	28,654	77,219
Total derivative assets	28,654	77,219
Total assets	29,824	88,608
Derivative liabilities:
Derivative liability, before netting		3,209
Net amounts of liabilities presented in the consolidated balance sheet		3,209
Total liabilities		3,209
Recurring basis | Level 1 | Related Party | PennyMac Mortgage Investment Trust
Derivative assets:
Investment in PennyMac Mortgage Investment Trust	1,101	1,121
Recurring basis | Level 1 | Call options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	3,301	66,176
Recurring basis | Level 1 | Call options on Eurodollar futures | Sales
Derivative liabilities:
Derivative liability, before netting		3,209
Recurring basis | Level 1 | Put options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	25,353	11,043
Recurring basis | Level 2
Assets:
Principal-only stripped mortgage-backed securities at fair value pledged to creditors	524,576
Loans held for sale	4,733,958	3,942,127
Derivative assets:
Derivative asset, before netting	42,479	91,277
Total derivative assets	42,479	91,277
Total assets	5,301,013	4,033,404
Derivative liabilities:
Derivative liability, before netting	41,698	97,937
Net amounts of liabilities presented in the consolidated balance sheet	41,698	97,937
Total liabilities	41,698	97,937
Recurring basis | Level 2 | Forward contracts | Purchases
Derivative assets:
Derivative asset, before netting	21,887	78,448
Derivative liabilities:
Derivative liability, before netting	6,049	5,141
Recurring basis | Level 2 | Forward contracts | Sales
Derivative assets:
Derivative asset, before netting	18,622	6,151
Derivative liabilities:
Derivative liability, before netting	35,649	92,796
Recurring basis | Level 2 | MBS put options
Derivative assets:
Derivative asset, before netting	1,970	413
Recurring basis | Level 2 | MBS call options
Derivative assets:
Derivative asset, before netting		6,265
Recurring basis | Level 3
Assets:
Loans held for sale	466,392	478,564
Derivative assets:
Derivative asset, before netting	74,545	90,313
Total derivative assets	74,545	90,313
Mortgage servicing rights	7,483,210	7,099,348
Total assets	8,024,147	7,668,225
Derivative liabilities:
Derivative liability, before netting	4,737	720
Net amounts of liabilities presented in the consolidated balance sheet	4,737	720
Mortgage servicing liabilities	1,732	1,805
Total liabilities	6,469	2,525
Recurring basis | Level 3 | Interest rate lock commitments
Derivative assets:
Derivative asset, before netting	74,545	90,313
Derivative liabilities:
Derivative liability, before netting	$ 4,737	$ 720