CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (120.8)	$ (102.6)	$ (6.8)
Other comprehensive income (loss):
Currency translation adjustments	10.5	(2.3)	(6.0)
Pension benefit adjustments	1.5	(5.1)	7.1
Deferred tax benefit (expense) on pension benefit adjustment	(0.4)	1.5	(2.1)
Amortization of net actuarial gains		(0.3)
Income tax on amortization of net actuarial gains		0.1
Comprehensive loss	(109.2)	(108.7)	(7.8)
Comprehensive income attributable to noncontrolling interest	0.9	0.3	0.1
Comprehensive loss attributable to Real Industry, Inc.	$ (110.1)	$ (109.0)	$ (7.9)