Intangible Assets (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 27, 2019	Jun. 28, 2018	Jun. 27, 2019	Jun. 28, 2018
Finite-Lived Intangible Assets [Line Items]
Common membership units issued, net of returned	1,044,665	2,821,710
Common membership units issued		3,736,860
Common membership units returned		915,150
Increase (decrease) in intangible assets, net	$ (7.6)	$ (15.9)
Integration and other encumbered payments, related parties - financing activities			$ 0.0	$ 11.5
AMC and Cinemark
Finite-Lived Intangible Assets [Line Items]
Increase (decrease) in intangible assets, net	(5.7)	(5.6)	(8.1)	(7.8)
Integration and other encumbered payments, related parties - financing activities	$ 2.5	$ 2.2	$ 10.6	$ 11.5
Minimum
Finite-Lived Intangible Assets [Line Items]
Percentage increase (decrease) in theater attendance for Common Unit adjustment to occur			(2.00%)
Maximum
Finite-Lived Intangible Assets [Line Items]
Percentage increase (decrease) in theater attendance for Common Unit adjustment to occur			2.00%

National CineMedia, LLC 10-Q