Short-Term Debt - Assets Sold Under Agreement to Repurchase (Details) - USD ($)			3 Months Ended
	Apr. 28, 2021	Dec. 19, 2016	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Apr. 01, 2020
Carrying value:
Net amounts of liabilities presented in the consolidated balance sheet			$ 3,336,577,000
Unamortized debt issuance costs and premiums			(3,133,000)		$ (4,625,000)
Total loans sold under agreements to repurchase			3,333,444,000		7,292,735,000
Servicing advances			230,395,000		232,107,000
PennyMac Holdings, L L C Repurchase Agreement
Carrying value:
Related Party Transaction, Maximum Principal Balance of Variable Funding Note		$ 1,000,000,000
Fannie Mae Repurchase Agreement
Carrying value:
Related Party Transaction, Maximum Principal Balance of Variable Funding Note	$ 1,000,000,000
FMSR VFN Repurchase Agreement
Carrying value:
Related Party Transaction, Maximum Principal Balance of Variable Funding Note	$ 250,000,000
Note Payable
During the period:
Average balance of assets sold under agreements to repurchase			1,300,000,000	$ 1,300,000,000
Carrying value:
Amortization of debt issuance costs			459,000	544,000
Loan Repo Facility
During the period:
Average balance of assets sold under agreements to repurchase			$ 3,722,179,000	$ 8,432,579,000
Weighted-average interest rate (as a percent)			2.19%	2.17%
Total interest expense			$ 23,770,000	$ 52,179,000
Maximum daily amount outstanding			7,289,147,000	10,856,677,000
Carrying value:
Unpaid principal balance under committed facilities			3,014,266,000		5,079,581,000
Unpaid principal balance under uncommitted facilities			322,311,000		2,217,779,000
Net amounts of liabilities presented in the consolidated balance sheet			3,336,577,000		7,297,360,000
Unamortized debt issuance costs			(3,133,000)		(4,625,000)
Total loans sold under agreements to repurchase			$ 3,333,444,000		$ 7,292,735,000
Weighted average interest rate (as a percent)			2.17%		1.83%
Available borrowing capacity committed			$ 2,350,734,000		$ 285,419,000
Available borrowing capacity uncommitted			10,512,689,000		8,417,221,000
Available borrowing capacity			12,863,423,000		8,702,640,000
Margin deposits placed with counterparties			10,875,000		10,875,000
Amortization of debt issuance costs			3,700,000	$ 6,200,000
Loan Repo Facility | Loans held for sale
Carrying value:
Fair value of assets pledged to secure			4,491,903,000		8,629,861,000
Loan Repo Facility | Mortgage servicing rights
Carrying value:
Fair value of assets pledged to secure			4,662,515,000		3,552,812,000
Loan Repo Facility | Servicing advances
Carrying value:
Fair value of assets pledged to secure			230,395,000		232,107,000
Loan Repo Facility | Deposits
Carrying value:
Fair value of assets pledged to secure			$ 36,106,000		$ 36,632,000
PLS | Credit Suisse First Boston Mortgage Capital LLC | Note Payable
Mortgage loans sold under agreement to repurchase
Maximum loan amount						$ 600,000,000