Short-Term Borrowings - Assets Sold Under Agreement to Repurchase (Details) - USD ($)			3 Months Ended		6 Months Ended
	Apr. 28, 2021	Dec. 19, 2016	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Apr. 01, 2020
During the period:
Total interest expense			$ 44,623,000	$ 17,487,000	$ 96,802,000	$ 43,171,000
Carrying value:
Unpaid principal balance			8,262,251,000		8,262,251,000
Unamortized debt issuance costs and premiums			(7,708,000)		(7,708,000)		$ (9,198,000)
Total loans sold under agreements to repurchase			8,254,543,000		8,254,543,000		9,654,797,000
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	1,300,000,000	1,300,000,000
Carrying value:
Amortization of debt issuance costs			634,000	451,000	1,200,000	896,000
Assets sold under agreements to repurchase
During the period:
Average balance of assets sold under agreements to repurchase			$ 7,571,340,000	$ 2,529,217,000	$ 7,999,580,000	$ 2,833,444,000
Weighted-average interest rate (as a percent)			2.07%	2.32%	2.13%	2.74%
Total interest expense			$ 44,623,000	$ 17,487,000	$ 96,802,000	$ 43,171,000
Maximum daily amount outstanding			10,856,677,000	3,769,495,000	10,856,677,000	3,769,495,000
Carrying value:
Unpaid principal balance			8,262,251,000		8,262,251,000		9,663,995,000
Unamortized debt issuance costs			(7,708,000)		(7,708,000)		(9,198,000)
Total loans sold under agreements to repurchase			$ 8,254,543,000		$ 8,254,543,000		$ 9,654,797,000
Weighted average interest rate (as a percent)			1.86%		1.86%		1.90%
Available borrowing capacity committed			$ 666,772,000		$ 666,772,000		$ 372,803,000
Available borrowing capacity uncommitted			6,695,976,000		6,695,976,000		2,163,202,000
Available borrowing capacity			7,362,748,000		7,362,748,000		2,536,005,000
Margin deposits placed with counterparties			10,875,000		10,875,000		5,625,000
Amortization of debt issuance costs			5,300,000	$ 2,800,000	11,800,000	$ 4,400,000
Assets sold under agreements to repurchase | Loans held for sale
Carrying value:
Fair value of assets pledged to secure			9,917,262,000		9,917,262,000		10,912,178,000
Assets sold under agreements to repurchase | Mortgage servicing rights
Carrying value:
Fair value of assets pledged to secure			3,209,383,000		3,209,383,000		2,490,267,000
Assets sold under agreements to repurchase | Servicing advances
Carrying value:
Fair value of assets pledged to secure			311,896,000		311,896,000		413,484,000
Assets sold under agreements to repurchase | Financing receivable
Carrying value:
Fair value of assets pledged to secure							80,862,000
Assets sold under agreements to repurchase | Deposits
Carrying value:
Fair value of assets pledged to secure			$ 49,934,000		$ 49,934,000		$ 153,054,000
PLS | Credit Suisse First Boston Mortgage Capital LLC | Note Payable
Mortgage loans sold under agreement to repurchase
Maximum loan amount								$ 600,000,000