Segment Information (Segment Revenues By Media) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Revenue from External Customer [Line Items]
Revenues	$ 1,256.1	$ 752.3	$ 639.5	$ 553.6	$ 791.2	$ 670.5	$ 476.8	$ 408.9	$ 3,201.5	$ 2,347.4	$ 2,399.6
Reportable Segments | Motion Pictures
Revenue from External Customer [Line Items]
Revenues									1,920.6	1,677.4	1,820.1
Reportable Segments | Motion Pictures | Theatrical
Revenue from External Customer [Line Items]
Revenues									371.3	314.1	354.0
Reportable Segments | Motion Pictures | Home Entertainment
Revenue from External Customer [Line Items]
Revenues									707.7	579.7	662.7
Reportable Segments | Motion Pictures | Television
Revenue from External Customer [Line Items]
Revenues									279.1	205.1	270.2
Reportable Segments | Motion Pictures | International
Revenue from External Customer [Line Items]
Revenues									533.8	548.2	495.0
Reportable Segments | Motion Pictures | Other
Revenue from External Customer [Line Items]
Revenues									28.7	30.3	38.2
Reportable Segments | Television Production
Revenue from External Customer [Line Items]
Revenues									837.4	669.9	579.5
Reportable Segments | Television Production | Home Entertainment
Revenue from External Customer [Line Items]
Revenues									39.9	60.3	44.8
Reportable Segments | Television Production | International
Revenue from External Customer [Line Items]
Revenues									149.1	190.2	112.4
Reportable Segments | Television Production | Other
Revenue from External Customer [Line Items]
Revenues									6.5	3.9	7.1
Reportable Segments | Television Production | Domestic Television
Revenue from External Customer [Line Items]
Revenues									641.9	415.5	415.2
Reportable Segments | Media Networks
Revenue from External Customer [Line Items]
Revenues									456.6	0.1	0.0
Reportable Segments | Media Networks | Starz Networks
Revenue from External Customer [Line Items]
Revenues									423.4	0.0	0.0
Reportable Segments | Media Networks | Content And Other
Revenue from External Customer [Line Items]
Revenues									30.3	0.0	0.0
Reportable Segments | Media Networks | Streaming Services
Revenue from External Customer [Line Items]
Revenues									2.9	0.1	0.0
Intersegment Eliminations
Revenue from External Customer [Line Items]
Revenues									(13.1)	0.0	0.0
Intersegment Eliminations | Motion Pictures
Revenue from External Customer [Line Items]
Revenues									(6.6)	0.0	0.0
Intersegment Eliminations | Television Production
Revenue from External Customer [Line Items]
Revenues									(5.6)	0.0	0.0
Intersegment Eliminations | Media Networks
Revenue from External Customer [Line Items]
Revenues									$ (0.9)	$ 0.0	$ 0.0