Related Party Transactions - Exchanged Private National Mortgage Acceptance Company, LLC Unitholders (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Transactions with Affiliates
Amount of tax benefits under the tax sharing agreement (as a percent)	85.00%
Payable to exchanged PNMAC unitholders under tax receivable agreement	$ 35.2		$ 35.2
Private National Mortgage Acceptance Company, LLC
Transactions with Affiliates
Payment of tax liability under the tax receivable agreement to Private National Mortgage Acceptance Company, LLC unitholders	$ 0.0	$ 0.0

Represents amounts payable to PennyMac's exchanged unitholders pursuant to an agreement under which an agreed-upon portion of the amount of the benefits, if any, that PFSI is deemed to realize as a result of (i) increases in tax basis of PennyMac's assets resulting from such unitholders' exchanges and (ii) certain other tax benefits related to entering into the tax receivable agreement, including tax benefits attributable to payments under the tax receivable agreement.

No definition available.

Name:	pfsi_PayableUnderTaxReceivableAgreementPayments
Namespace Prefix:	pfsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant