Net Income (Loss) Per Share (Diluted) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017		Dec. 31, 2016
Numerator:
Net income (loss) attributable to Lions Gate Entertainment Corp. shareholders	$ 193.0	$ (30.6)	$ 382.3		$ (46.8)
Interest on convertible notes, net of tax	0.1	0.0	0.4		0.0
Numerator for diluted net income (loss) per common share	$ 193.1	$ (30.6)	$ 382.7		$ (46.8)
Denominator:
Weighted average common shares outstanding (in shares)	208.8	161.4	207.8	[1]	152.2	[1]
Effect of dilutive securities:
Conversion of notes (in shares)	2.1	0.0	2.1		0.0
Share purchase options (in shares)	8.4	0.0	7.5		0.0
Restricted share units and restricted stock (in shares)	0.7	0.0	0.7		0.0
Contingently issuable shares	1.6	0.0	1.6		0.0
Adjusted weighted average common shares outstanding	221.6	161.4	219.7		152.2
Diluted net income (loss) per common share (in usd per share)	$ 0.87	$ (0.19)	$ 1.74		$ (0.31)

[1] The weighted average common shares outstanding for the three months ended December 31, 2017 do not include the equity portion of the merger consideration related to the dissenting Starz shareholders as discussed in Note 2 and Note 15.