Fair Value - Level 3 Unobservable Inputs, ESS (Details) - Excess servicing spread financing - Level 3 $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2018 USD ($) item	Dec. 31, 2017 USD ($) item
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Carrying value \| $	$ 223,275	$ 236,534
Unpaid principal balance of underlying mortgage loans \| $	$ 24,058,366	$ 27,217,199
Average servicing fee rate (as a percent)	0.34%	0.34%
Average excess servicing spread (as a percent)	0.19%	0.19%
Pricing spread \| Minimum
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Input	3.4	3.8
Pricing spread \| Maximum
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Input	3.9	4.3
Pricing spread \| Weighted average
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Input	3.7	4.1
Annual total prepayment speed \| Minimum
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Input	7.6	8.4
Annual total prepayment speed \| Maximum
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Input	38.4	41.4
Annual total prepayment speed \| Weighted average
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Input	9.0	10.8
Life \| Minimum
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Input	1.4	1.4
Life \| Maximum
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Input	8.0	7.7
Life \| Weighted average
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Input	7.1	6.5

Represents the amortized cost of the unpaid principal balance of underlying loans.

No definition available.

Name:	pfsi_AmortizedCostUnpaidPrincipalBalanceOfUnderlyingLoans
Namespace Prefix:	pfsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Average excess servicing spread on financial assets of a securitization, asset-backed financing arrangement, or similar transfer regardless of when the transfer occurred.

+ References

No definition available.

+ Details

Name:	pfsi_AssumptionForFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesAverageExcessServicingSpread
Namespace Prefix:	pfsi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Average servicing fee rate on financial assets of a securitization, asset-backed financing arrangement, or similar transfer regardless of when the transfer occurred.

+ References

No definition available.

+ Details

Name:	pfsi_AssumptionForFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesAverageServicingFeeRate
Namespace Prefix:	pfsi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Value of input used to measure investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleMeasurementInput
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

The carrying amount (fair value) as of the balance sheet date of the transferor's interests in transferred financial assets (typically securitized receivables, generally not involved in the collection of principal) following transfer of significant portions of such financial instruments to other parties. Such interests could be ancillary cash flows and interest-only strips.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=109247956&loc=d3e107314-111719

+ Details

Name:	us-gaap_InterestsContinuedToBeHeldByTransferorFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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

- Details

Name:	us-gaap_FinancialInstrumentAxis=pfsi_ExcessServicingSpreadFinancingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MeasurementInputTypeAxis=pfsi_MeasurementInputPricingSpreadMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_WeightedAverageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MeasurementInputTypeAxis=pfsi_MeasurementInputAnnualTotalPrepaymentSpeedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MeasurementInputTypeAxis=pfsi_MeasurementInputLifeOfLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: