Fair Value - Financial Statement Items Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Assets:
Short-term investment at fair value	$ 78,006	$ 6,873
Loans held for sale	5,119,234	9,742,483
Derivative assets:
Derivative asset, before netting	556,172	398,672
Netting	(331,101)	(64,977)
Total derivative assets	225,071	333,695
Investment in PennyMac Mortgage Investment Trust	1,267	1,300
Derivative liabilities:
Derivative liability, before netting	246,388	54,702
Netting	(155,551)	(32,096)
Net amounts of liabilities presented in the consolidated balance sheet	90,837	22,606
Mortgage servicing liabilities	2,564	2,816
Interest rate lock commitments
Derivative assets:
Total derivative assets	79,717	323,473
Forward contracts | Purchases
Derivative assets:
Derivative asset, before netting	21,152	20,485
Derivative liabilities:
Derivative liability, before netting	162,584	18,007
Forward contracts | Sales
Derivative assets:
Derivative asset, before netting	316,856	40,215
Derivative liabilities:
Derivative liability, before netting	35,283	35,415
MBS put options
Derivative assets:
Derivative asset, before netting	43,543	7,655
Call options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	1,684	2,078
Put options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	93,220	3,141
Put options on Eurodollar futures | Sales
Derivative liabilities:
Derivative liability, before netting	6,703
Level 3
Assets:
Loans held for sale	776,590	1,128,876
Level 3 | Interest rate lock commitments
Assets:
Loans held for sale	37,899	322,193
Recurring basis
Assets:
Short-term investment at fair value	78,006	6,873
Loans held for sale	5,119,234	9,742,483
Derivative assets:
Derivative asset, before netting	556,172	398,672
Netting	(331,101)	(64,977)
Total derivative assets	225,071	333,695
Mortgage servicing rights at fair value	4,707,039	3,878,078
Total assets	10,130,617	13,962,429
Derivative liabilities:
Derivative liability, before netting	246,388	54,702
Netting	(155,551)	(32,096)
Net amounts of liabilities presented in the consolidated balance sheet	90,837	22,606
Mortgage servicing liabilities	2,564	2,816
Total liabilities	93,401	25,422
Recurring basis | PennyMac Mortgage Investment Trust
Derivative assets:
Investment in PennyMac Mortgage Investment Trust	1,267	1,300
Recurring basis | Interest rate lock commitments
Derivative assets:
Derivative asset, before netting	79,717	323,473
Derivative liabilities:
Derivative liability, before netting	41,818	1,280
Recurring basis | Forward contracts | Purchases
Derivative assets:
Derivative asset, before netting	21,152	20,485
Derivative liabilities:
Derivative liability, before netting	162,584	18,007
Recurring basis | Forward contracts | Sales
Derivative assets:
Derivative asset, before netting	316,856	40,215
Derivative liabilities:
Derivative liability, before netting	35,283	35,415
Recurring basis | MBS put options
Derivative assets:
Derivative asset, before netting	43,543	7,655
Recurring basis | Swaptions | Purchases
Derivative assets:
Derivative asset, before netting		1,625
Recurring basis | Call options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	1,684	2,078
Recurring basis | Put options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	93,220	3,141
Recurring basis | Put options on Eurodollar futures | Sales
Derivative liabilities:
Derivative liability, before netting	6,703
Recurring basis | Level 1
Assets:
Short-term investment at fair value	78,006	6,873
Derivative assets:
Derivative asset, before netting	94,904	5,219
Total derivative assets	94,904	5,219
Total assets	174,177	13,392
Derivative liabilities:
Derivative liability, before netting	6,703
Net amounts of liabilities presented in the consolidated balance sheet	6,703
Total liabilities	6,703
Recurring basis | Level 1 | PennyMac Mortgage Investment Trust
Derivative assets:
Investment in PennyMac Mortgage Investment Trust	1,267	1,300
Recurring basis | Level 1 | Call options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	1,684	2,078
Recurring basis | Level 1 | Put options on Eurodollar futures | Purchases
Derivative assets:
Derivative asset, before netting	93,220	3,141
Recurring basis | Level 1 | Put options on Eurodollar futures | Sales
Derivative liabilities:
Derivative liability, before netting	6,703
Recurring basis | Level 2
Assets:
Loans held for sale	4,342,644	8,613,607
Derivative assets:
Derivative asset, before netting	381,551	69,980
Total derivative assets	381,551	69,980
Total assets	4,724,195	8,683,587
Derivative liabilities:
Derivative liability, before netting	197,867	53,422
Net amounts of liabilities presented in the consolidated balance sheet	197,867	53,422
Total liabilities	197,867	53,422
Recurring basis | Level 2 | Forward contracts | Purchases
Derivative assets:
Derivative asset, before netting	21,152	20,485
Derivative liabilities:
Derivative liability, before netting	162,584	18,007
Recurring basis | Level 2 | Forward contracts | Sales
Derivative assets:
Derivative asset, before netting	316,856	40,215
Derivative liabilities:
Derivative liability, before netting	35,283	35,415
Recurring basis | Level 2 | MBS put options
Derivative assets:
Derivative asset, before netting	43,543	7,655
Recurring basis | Level 2 | Swaptions | Purchases
Derivative assets:
Derivative asset, before netting		1,625
Recurring basis | Level 3
Assets:
Loans held for sale	776,590	1,128,876
Derivative assets:
Derivative asset, before netting	79,717	323,473
Total derivative assets	79,717	323,473
Mortgage servicing rights at fair value	4,707,039	3,878,078
Total assets	5,563,346	5,330,427
Derivative liabilities:
Derivative liability, before netting	41,818	1,280
Net amounts of liabilities presented in the consolidated balance sheet	41,818	1,280
Mortgage servicing liabilities	2,564	2,816
Total liabilities	44,382	4,096
Recurring basis | Level 3 | Interest rate lock commitments
Derivative assets:
Derivative asset, before netting	79,717	323,473
Derivative liabilities:
Derivative liability, before netting	$ 41,818	$ 1,280