Investment In Films and Television Programs and Program Rights (Investment in Films and Television Programs and Licensed Program Rights) (Details) $ in Millions	Sep. 30, 2020 USD ($)
Individual Monetization
Released, net of accumulated amortization	$ 395.9
Completed and not released	133.4
In progress	133.3
In development	91.0
Total	753.6
Film Group Monetization
Released, net of accumulated amortization	284.6
Completed and not released	0.0
In progress	191.4
In development	40.2
Total	516.2
Licensed program rights, net of accumulated amortization	493.4
Investment in films and television programs and program rights, net	$ 1,763.2

Film, Monetized on Its Own and Film, Monetized in Film Group and License Agreement for Program Rights, Capitalized Cost

No definition available.

Name:	lgfa_FilmMonetizedonItsOwnandFilmMonetizedinFilmGroupandLicenseAgreementforProgramRightsCapitalizedCost
Namespace Prefix:	lgfa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of capitalized cost for right acquired by broadcaster under license agreement for program material.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 920
-SubTopic 350
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=120154842&loc=d3e47862-107914

+ Details

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

- Definition

Amount of capitalized film cost for film predominantly monetized with other films and license agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 926
-SubTopic 20
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=120154696&loc=d3e54431-107959

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount of capitalized film cost for completed and not released film predominantly monetized with other films and license agreements.

+ References

+ Details

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

- Definition

Amount of capitalized film cost incurred in development and preproduction of film predominantly monetized with other films and license agreements.

+ References

+ Details

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

- Definition

Amount of capitalized film cost incurred in production of film predominantly monetized with other films and license agreements.

+ References

+ Details

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

- Definition

Amount of capitalized film cost for released film predominantly monetized with other films and license agreements.

+ References

+ Details

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

- Definition

Amount of capitalized film cost for film predominantly monetized on its own.

+ References

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount of capitalized film cost for completed and not released film predominantly monetized on its own.

+ References

+ Details

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

- Definition

Amount of capitalized film cost incurred in development and preproduction of film predominantly monetized on its own.

+ References

+ Details

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

- Definition

Amount of capitalized film cost incurred in production of film predominantly monetized on its own.

+ References

+ Details

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

- Definition

Amount of capitalized film cost for released film predominantly monetized on its own.

+ References

+ Details

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