Leases Leases (Schedule of lease cost) (Details) - USD ($) $ in Millions	12 Months Ended
Jan. 01, 2021	Jan. 03, 2020
Leases [Abstract]
Amortization of ROU assets	$ 9	$ 8
Interest on lease liabilities	0	1
Finance lease cost	9	9
Operating lease cost	169	155
Variable lease cost	103	107
Short-term lease cost	8	7
Less: Sublease income	(11)	(6)
Total lease cost	278	272
ROU lease expense	$ 145	$ 136

Finance Lease Cost

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Operating Lease, Right-of-Use Asset, Lease Expense

+ References

No definition available.

+ Details

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Namespace Prefix:	ldos_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of interest expense on finance lease liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918686-209980

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 55
-Paragraph 53
-URI http://asc.fasb.org/extlink&oid=121568110&loc=SL77918982-209971

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of amortization expense attributable to right-of-use asset from finance lease.

+ References

+ Details

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

- Definition

Amount of lease cost recognized by lessee for lease contract.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
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-URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918686-209980

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+ Details

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Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

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- Definition

Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 55
-Paragraph 53
-URI http://asc.fasb.org/extlink&oid=121568110&loc=SL77918982-209971

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918686-209980

+ Details

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Balance Type:	debit
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- Definition

Amount of short-term lease cost, excluding expense for lease with term of one month or less.

+ References

+ Details

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Period Type:	duration

- Definition

Amount of sublease income excluding finance and operating lease expense.

+ References

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Amount of variable lease cost, excluded from lease liability, recognized when obligation for payment is incurred for finance and operating leases.

+ References

+ Details

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