Leases (Narrative) (Details) $ in Millions	12 Months Ended
	Mar. 31, 2021 USD ($) renewal_period	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Decrease in finance lease right-of-use asset due to a reassessment event	$ (42.0)	$ 0.0
Decrease in finance lease liability due to a reassessment event	(48.6)	0.0
Operating leases - increase in right-of-use assets	6.0	0.0
Operating leases - increase in lease liability	$ 12.6	$ 0.0
Operating leases, rent expense			$ 27.0
Maximum
Lessee, Lease, Description [Line Items]
Leases, remaining lease term	10 years
Building
Lessee, Lease, Description [Line Items]
Operating lease, number of successive renewal periods available for Starz building lease | renewal_period	4
Operating lease, renewal term (in years)	5 years
Studio Facility
Lessee, Lease, Description [Line Items]
Lease not yet commenced, term (in years)	10 years 6 months
Lease not yet commenced, renewal term (in years)	5 years
Lease not yet commenced, total minimum lease payments	$ 72.8
Office Space
Lessee, Lease, Description [Line Items]
Lease not yet commenced, term (in years)	10 years 6 months
Lease not yet commenced, total minimum lease payments	$ 11.7