Short-Term Debt - Assets Sold Under Agreement to Repurchase (Details) - USD ($)			3 Months Ended		9 Months Ended
	Apr. 28, 2021	Dec. 19, 2016	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Dec. 07, 2021
Carrying value:
Net amounts of liabilities presented in the consolidated balance sheet			$ 3,490,082,000		$ 3,490,082,000
Total loans sold under agreements to repurchase			3,487,335,000		3,487,335,000		$ 7,292,735,000
Servicing advances			253,370,000		253,370,000		232,107,000
PennyMac Holdings, L L C Repurchase Agreement
Carrying value:
Related Party Transaction, Maximum Principal Balance of Variable Funding Note		$ 2,000,000,000
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			1,800,000,000	$ 1,300,000,000	1,510,623,000	$ 1,300,000,000
Carrying value:
Amortization of debt issuance costs			726,000	570,000	1,700,000	1,700,000
Freddie Mac MSR Facility
Carrying value:
Amount Of Repurchase Agreement								$ 175,000,000
Loan Repo Facility
During the period:
Average balance of assets sold under agreements to repurchase			$ 1,949,452,000	$ 6,031,491,000	$ 2,622,581,000	$ 7,336,341,000
Weighted-average interest rate (as a percent)			4.34%	2.11%	2.90%	2.12%
Total interest expense			$ 24,329,000	$ 35,783,000	$ 67,048,000	$ 132,585,000
Maximum daily amount outstanding			3,490,082,000	8,044,148,000	7,289,147,000	10,969,029,000
Carrying value:
Unpaid principal balance under committed facilities			2,703,673,000		2,703,673,000		5,079,581,000
Unpaid principal balance under uncommitted facilities			786,409,000		786,409,000		2,217,779,000
Net amounts of liabilities presented in the consolidated balance sheet			3,490,082,000		3,490,082,000		7,297,360,000
Unamortized debt issuance costs			(2,747,000)		(2,747,000)		(4,625,000)
Total loans sold under agreements to repurchase			$ 3,487,335,000		$ 3,487,335,000		$ 7,292,735,000
Weighted average interest rate (as a percent)			4.66%		4.66%		1.83%
Available borrowing capacity committed			$ 801,328,000		$ 801,328,000		$ 285,419,000
Available borrowing capacity uncommitted			5,333,590,000		5,333,590,000		8,417,221,000
Available borrowing capacity			6,134,918,000		6,134,918,000		8,702,640,000
Amortization of debt issuance costs			3,000,000.0	$ 3,700,000	10,100,000	$ 15,500,000
Loan Repo Facility | Loans held for sale
Carrying value:
Fair value of assets pledged to secure			3,626,320,000		3,626,320,000		8,629,861,000
Loan Repo Facility | Mortgage servicing rights
Carrying value:
Fair value of assets pledged to secure			5,604,447,000		5,604,447,000		3,552,812,000
Loan Repo Facility | Servicing advances
Carrying value:
Fair value of assets pledged to secure			253,370,000		253,370,000		232,107,000
Loan Repo Facility | Deposits
Carrying value:
Fair value of assets pledged to secure			$ 9,886,000		$ 9,886,000		$ 36,632,000