Computation of Basic and Diluted Earnings (loss) Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share [Abstract]
Loss from continuing operations	$ (1.3)	$ (13.7)	$ (11.3)	$ (31.5)
Earnings from discontinued operations, net of income taxes	0.1	2.9	0.1	27.2
Net loss	(1.2)	(10.8)	(11.2)	(4.3)
Earnings from continuing operations attributable to noncontrolling interest	0.3	0.1	0.4	0.2
Net loss attributable to Real Industry, Inc.	(1.5)	(10.9)	(11.6)	(4.5)
Dividends on Redeemable Preferred Stock, in-kind	(0.5)	(0.5)	(0.9)	(0.6)
Accretion of fair value adjustment to Redeemable Preferred Stock	(0.2)	(0.2)	(0.5)	(0.3)
Net loss available to common stockholders	$ (2.2)	$ (11.6)	$ (13.0)	$ (5.4)
Denominator for basic and diluted earnings (loss) per share—Weighted average shares outstanding	29,252,343	27,631,795	29,160,245	24,689,253
Basic and diluted earnings (loss) per share:
Continuing operations	$ (0.08)	$ (0.53)	$ (0.43)	$ (1.32)
Discontinued operations	0.01	0.11		1.10
Basic and diluted loss per share	$ (0.07)	$ (0.42)	$ (0.43)	$ (0.22)