Transactions with Related Parties - Summary of Mortgage Loan Servicing Fees Earned and Mortgage Servicing Rights Recaptured Income Earned (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Related Party Transaction [Line Items]
Mortgage loan servicing fees	$ 11,453	$ 10,670
MSR recapture income recognized included in Net mortgage loan servicing fees	130	0
Average mortgage loan servicing portfolio	43,253,977	34,599,043
Penny Mac Loan Services LLC [Member]
Related Party Transaction [Line Items]
Mortgage loan servicing fees	11,453	10,670
MSR recapture income recognized included in Net mortgage loan servicing fees	130	0
Average mortgage loan servicing portfolio	43,253,977	34,599,043
Penny Mac Loan Services LLC [Member] \| Mortgage loans acquired for sale at fair value [Member]
Related Party Transaction [Line Items]
Mortgage loan servicing fees	171	57
Average mortgage loan servicing portfolio	918,741	756,646
Penny Mac Loan Services LLC [Member] \| Mortgage loans acquired for sale at fair value [Member] \| Base [Member]
Related Party Transaction [Line Items]
Mortgage loan servicing fees	56	26
Penny Mac Loan Services LLC [Member] \| Mortgage loans acquired for sale at fair value [Member] \| Activity-based [Member]
Related Party Transaction [Line Items]
Mortgage loan servicing fees	115	31
Penny Mac Loan Services LLC [Member] \| Distressed mortgage loans [Member]
Related Party Transaction [Line Items]
Mortgage loan servicing fees	6,808	6,926
Average mortgage loan servicing portfolio	2,064,101	2,309,282
Penny Mac Loan Services LLC [Member] \| Distressed mortgage loans [Member] \| Base [Member]
Related Party Transaction [Line Items]
Mortgage loan servicing fees	3,359	4,032
Penny Mac Loan Services LLC [Member] \| Distressed mortgage loans [Member] \| Activity-based [Member]
Related Party Transaction [Line Items]
Mortgage loan servicing fees	3,449	2,894
Penny Mac Loan Services LLC [Member] \| Mortgage loans held in VIE [Member]
Related Party Transaction [Line Items]
Mortgage loan servicing fees	41	30
Average mortgage loan servicing portfolio	454,538	526,220
Penny Mac Loan Services LLC [Member] \| Mortgage loans held in VIE [Member] \| Base [Member]
Related Party Transaction [Line Items]
Mortgage loan servicing fees	41	30
Penny Mac Loan Services LLC [Member] \| Mortgage loans held in VIE [Member] \| Activity-based [Member]
Related Party Transaction [Line Items]
Mortgage loan servicing fees	0	0
Penny Mac Loan Services LLC [Member] \| Mortgage servicing rights [Member]
Related Party Transaction [Line Items]
Mortgage loan servicing fees	4,433	3,657
Penny Mac Loan Services LLC [Member] \| Mortgage servicing rights [Member] \| Base [Member]
Related Party Transaction [Line Items]
Mortgage loan servicing fees	4,344	3,626
Penny Mac Loan Services LLC [Member] \| Mortgage servicing rights [Member] \| Activity-based [Member]
Related Party Transaction [Line Items]
Mortgage loan servicing fees	$ 89	$ 31

Average unpaid principal balance of mortgage loans in the mortgage loan servicing portfolio.

No definition available.

Name:	pmt_AverageBalanceDuringPeriodForServicingAssetsPortfolio
Namespace Prefix:	pmt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents MSR recapture earned from an affiliate under a recapture agreement during the period. Recapture amounts represent fees earned relating to mortgage loans subject to existing excess servicing spread that are refinanced by the affiliate.

+ References

No definition available.

+ Details

Name:	pmt_MortgageServicingRightsRecaptureFromAffiliate
Namespace Prefix:	pmt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The loan servicing fees paid to third parties that relate to loan expenses for a portfolio containing the entire group of loans owned by the company.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

Name:	us-gaap_LoanPortfolioExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=pmt_PennyMacLoanServicesLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=pmt_MortgageLoansAcquiredForSaleAtFairValueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateLoanTypeAxis=pmt_BaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateLoanTypeAxis=pmt_ActivityBasedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=pmt_MortgageLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=pmt_MortgageLoansHeldByVariableInterestEntityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=pmt_MortgageServicingRightsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: