Contingencies (Narrative) (Details) shares in Millions, $ in Millions				1 Months Ended	3 Months Ended			9 Months Ended
		Nov. 08, 2018 USD ($)	Oct. 09, 2018 USD ($)	Aug. 30, 2016 class_action_complaint	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)	Mar. 16, 2017 plaintiff	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)	Nov. 05, 2018 USD ($)	Dec. 08, 2016 USD ($)
Loss Contingencies [Line Items]
Shareholder litigation settlements	[1]				$ 0.0	$ 0.0		$ 114.1	$ 0.0
Petitions for appraisal filed | plaintiff							5
Starz Dissenting Shareholders | Starz
Loss Contingencies [Line Items]
Outstanding equity interests (in shares) | shares					22.5			22.5
Fiduciary Litigation
Loss Contingencies [Line Items]
Number of plaintiffs | class_action_complaint				7
Settlement payment amount			$ 92.5					$ 92.5
Insurance reimbursement, amount								37.8
Shareholder litigation settlements								54.8
Lawsuit for insurance reimbursement, amount										$ 10.0
Appraisal Litigation
Loss Contingencies [Line Items]
Settlement payment amount		$ 964.0						964.0
Shareholder litigation settlements								$ 59.3
Value of original merger consideration, dissenting shareholders liability accrued at time of acquisition											$ 797.3

[1] Shareholder litigation settlements of $114.1 million in the nine months ended December 31, 2018 includes the following: (i) $54.8 million for the net expense recorded for the settlement of the Fiduciary Litigation (representing the settlement amount of $92.5 million, net of aggregate insurance reimbursement of $37.8 million and (ii) $59.3 million related to the Appraisal Litigation, representing the amount by which the settlement amount of approximately $964 million exceeds the previously accrued dissenting shareholders' liability including interest through the date agreed in the settlement. See Note 16.