Contract Assets and Contract Liabilities - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 26, 2021	Sep. 27, 2020	Sep. 26, 2021	Sep. 27, 2020
Revenue from Contract with Customer [Abstract]
Increase (decrease) in contract assets			$ (2.2)
Increase (decrease) in contract liabilities			(0.3)
Recognition of contract liabilities	$ 5.9	$ 1.2	$ 89.5	$ 34.6

Increase (Decrease) in Contract with Customer, Liability, Including Foreign Currency Exchange Effects

No definition available.

Name:	pae_IncreaseDecreaseInContractWithCustomerLiabilityIncludingForeignCurrencyExchangeEffects
Namespace Prefix:	pae_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130549-203045

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of increase (decrease) in right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

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