Line Of Credit Facility, Minimum Borrowing Capacity

No definition available.

Name:	mant_LineOfCreditFacilityMinimumBorrowingCapacity
Namespace Prefix:	mant_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt issuance costs related to line of credit arrangements. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section S45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=68176171&loc=SL68176184-208336

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=mant_BankofAmericaSyndicateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
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:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
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:	us-gaap_CreditFacilityAxis=mant_TermLoanFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Subsequent Events (Narrative) (Details) - USD ($)		6 Months Ended
Subsequent Events (Narrative) (Details) - USD ($)	Jul. 20, 2021	Jun. 30, 2021
Subsequent Event
Subsequent Event [Line Items]
Debt Issuance Costs, Line of Credit Arrangements, Net	$ 3,300,000
Bank of America Syndicate [Member] \| Subsequent Event
Subsequent Event [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,100,000,000
Revolving Credit Facility [Member] \| Minimum [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Subsequent Event [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.25%
Revolving Credit Facility [Member] \| Minimum [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Subsequent Event
Subsequent Event [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.25%
Revolving Credit Facility [Member] \| Minimum [Member] \| Bank of America's Base Rate [Member]
Subsequent Event [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.25%
Revolving Credit Facility [Member] \| Minimum [Member] \| Bank of America's Base Rate [Member] \| Subsequent Event
Subsequent Event [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.25%
Revolving Credit Facility [Member] \| Maximum [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Subsequent Event [Line Items]
Debt Instrument, Basis Spread on Variable Rate		2.25%
Revolving Credit Facility [Member] \| Maximum [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Subsequent Event
Subsequent Event [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.00%
Revolving Credit Facility [Member] \| Maximum [Member] \| Bank of America's Base Rate [Member]
Subsequent Event [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.25%
Revolving Credit Facility [Member] \| Maximum [Member] \| Bank of America's Base Rate [Member] \| Subsequent Event
Subsequent Event [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.00%
Revolving Credit Facility [Member] \| Bank of America Syndicate [Member]
Subsequent Event [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 500,000,000
Revolving Credit Facility [Member] \| Bank of America Syndicate [Member] \| Subsequent Event
Subsequent Event [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 500,000,000
Term Loan Facility [Member] \| Bank of America Syndicate [Member] \| Subsequent Event
Subsequent Event [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	600,000,000
Line Of Credit Facility, Minimum Borrowing Capacity	$ 50,000,000