Consolidating Financial Information - Convertible Senior Subordinated Notes (Statement of Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Consolidating Financial Information [Line Items]
Net income (loss)	$ 191.1	$ (30.5)	$ 378.5	$ (47.0)
Foreign currency translation adjustments, net of tax	0.5	(2.3)	2.1	(7.8)
Net unrealized gain (loss) on available-for-sale securities, net of tax	(2.3)	32.4	0.8	55.3
Reclassification adjustment for gain on available-for-sale securities realized in net loss	0.0	(20.4)	0.0	(20.4)
Net unrealized loss on foreign exchange contracts, net of tax	(0.3)	(1.9)	(0.5)	(4.9)
Comprehensive income (loss)	189.0	(22.7)	380.9	(24.8)
Less: Comprehensive (income) loss attributable to noncontrolling interests	1.9	(0.1)	3.8	0.2
Comprehensive income (loss) attributable to Lions Gate Entertainment Corp. shareholders	$ 190.9	$ (22.8)	384.7	(24.6)
Convertible Senior Subordinated Notes
Consolidating Financial Information [Line Items]
Net income (loss)			378.5	(47.0)
Foreign currency translation adjustments, net of tax			2.1	(7.8)
Net unrealized gain (loss) on available-for-sale securities, net of tax			0.8	55.3
Reclassification adjustment for gain on available-for-sale securities realized in net loss				(20.4)
Net unrealized loss on foreign exchange contracts, net of tax			(0.5)	(4.9)
Comprehensive income (loss)			380.9	(24.8)
Less: Comprehensive (income) loss attributable to noncontrolling interests			3.8	0.2
Comprehensive income (loss) attributable to Lions Gate Entertainment Corp. shareholders			384.7	(24.6)
Convertible Senior Subordinated Notes \| Consolidating Adjustments
Consolidating Financial Information [Line Items]
Net income (loss)			(541.3)	117.5
Foreign currency translation adjustments, net of tax			(2.5)	23.5
Net unrealized gain (loss) on available-for-sale securities, net of tax			(0.7)	(55.3)
Reclassification adjustment for gain on available-for-sale securities realized in net loss				20.4
Net unrealized loss on foreign exchange contracts, net of tax			0.5	4.9
Comprehensive income (loss)			(544.0)	111.0
Less: Comprehensive (income) loss attributable to noncontrolling interests			(0.3)	0.2
Comprehensive income (loss) attributable to Lions Gate Entertainment Corp. shareholders			(544.3)	111.2
Convertible Senior Subordinated Notes \| Lions Gate Entertainment Corp. \| Reportable Legal Entities
Consolidating Financial Information [Line Items]
Net income (loss)			382.1	(46.8)
Foreign currency translation adjustments, net of tax			2.1	(7.8)
Net unrealized gain (loss) on available-for-sale securities, net of tax			0.8	55.3
Reclassification adjustment for gain on available-for-sale securities realized in net loss				(20.4)
Net unrealized loss on foreign exchange contracts, net of tax			(0.5)	(4.9)
Comprehensive income (loss)			384.5	(24.6)
Less: Comprehensive (income) loss attributable to noncontrolling interests			0.0	0.0
Comprehensive income (loss) attributable to Lions Gate Entertainment Corp. shareholders			384.5	(24.6)
Convertible Senior Subordinated Notes \| Lions Gate Entertainment Inc. \| Reportable Legal Entities
Consolidating Financial Information [Line Items]
Net income (loss)			25.8	(159.1)
Foreign currency translation adjustments, net of tax			1.7	(13.6)
Net unrealized gain (loss) on available-for-sale securities, net of tax			1.2	0.0
Reclassification adjustment for gain on available-for-sale securities realized in net loss				0.0
Net unrealized loss on foreign exchange contracts, net of tax			0.0	0.0
Comprehensive income (loss)			28.7	(172.7)
Less: Comprehensive (income) loss attributable to noncontrolling interests			0.0	0.0
Comprehensive income (loss) attributable to Lions Gate Entertainment Corp. shareholders			28.7	(172.7)
Convertible Senior Subordinated Notes \| Non-guarantor Subsidiaries \| Reportable Legal Entities
Consolidating Financial Information [Line Items]
Net income (loss)			511.9	41.4
Foreign currency translation adjustments, net of tax			0.8	(9.9)
Net unrealized gain (loss) on available-for-sale securities, net of tax			(0.5)	55.3
Reclassification adjustment for gain on available-for-sale securities realized in net loss				(20.4)
Net unrealized loss on foreign exchange contracts, net of tax			(0.5)	(4.9)
Comprehensive income (loss)			511.7	61.5
Less: Comprehensive (income) loss attributable to noncontrolling interests			4.1	0.0
Comprehensive income (loss) attributable to Lions Gate Entertainment Corp. shareholders			$ 515.8	$ 61.5

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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