UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (40.5)	$ (10.8)	$ (58.0)	$ (22.0)
Other comprehensive income (loss):
Currency translation adjustments	3.5	0.5	9.2	1.8
Amortization of net actuarial gains				(0.1)
Comprehensive loss	(37.0)	(10.3)	(48.8)	(20.3)
Comprehensive income attributable to noncontrolling interest	0.3	0.1	0.7	0.5
Comprehensive loss attributable to Real Industry, Inc.	$ (37.3)	$ (10.4)	$ (49.5)	$ (20.8)