Business Acquisition, Equity Interest Issued or Issuable, Percentage Of Number of Shares Outstanding

No definition available.

Name:	prsp_BusinessAcquisitionEquityInterestIssuedorIssuablePercentageOfNumberofSharesOutstanding
Namespace Prefix:	prsp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Payments To Acquire Business, Debt Extinguishment

+ References

No definition available.

+ Details

Name:	prsp_PaymentsToAcquireBusinessDebtExtinguishment
Namespace Prefix:	prsp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number of shares of equity interests issued or issuable to acquire entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

+ Details

Name:	us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued
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Data Type:	xbrli:sharesItemType
Balance Type:	na
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_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109124213&loc=d3e6613-128477

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109124213&loc=d3e6578-128477

+ Details

Name:	us-gaap_BusinessCombinationConsiderationTransferred1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of equity interests of the acquirer, including instruments or interests issued or issuable in consideration for the business combination.

+ References

+ Details

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

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireBusinessesGross
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

+ Details

Name:	us-gaap_SharePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_BusinessAcquisitionAxis=prsp_VencoreHoldingCorp.andKGSHoldingCorp.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=prsp_VencoreHoldingCorpMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=prsp_KGSHoldingCorp.Member
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Acquisitions - Schedule of Consideration Exchanged (Details) - USD ($) $ / shares in Units, $ in Millions		6 Months Ended
	May 31, 2018	Sep. 30, 2018	Sep. 30, 2017
Business Acquisition [Line Items]
Preliminary fair value of cash consideration paid by USPS to extinguish certain existing Vencore indebtedness		$ 994	$ 0
Closing price (in dollars per share)	$ 24.86
Vencore and KeyPoint
Business Acquisition [Line Items]
Preliminary fair value of cash purchase consideration received by Vencore Stockholders	$ 400
Preliminary fair value of cash consideration paid by USPS to extinguish certain existing Vencore indebtedness	$ 1,000
Shares issued in a business acquisition as a percentage of outstanding shares	14.00%
Vencore
Business Acquisition [Line Items]
Preliminary fair value of equity purchase consideration received by Vencore Stockholders	$ 578
Preliminary fair value of cash purchase consideration received by Vencore Stockholders	400
Preliminary fair value of cash consideration paid by USPS to extinguish certain existing Vencore indebtedness	994
Consideration transferred	$ 1,972
Number of shares issued in a business acquisition	18,877,244
KeyPoint
Business Acquisition [Line Items]
Number of shares issued in a business acquisition	4,396,097