Computation of Basic and Diluted Earnings (loss) Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Loss from continuing operations	$ (10.0)	$ (17.5)
Earnings (loss) from discontinued operations, net of income taxes		24.3
Net earnings (loss)	(10.0)	6.8
Earnings (loss) from continuing operations attributable to noncontrolling interest	0.1	0.1
Net earnings (loss) attributable to Real Industry, Inc.	(10.1)	6.7
Dividends and accretion on Redeemable Preferred Stock	(0.7)	(0.2)
Net earnings (loss) available to common stockholders	$ (10.8)	$ 6.5
Denominator for basic and diluted earnings (loss) per share— Weighted average shares outstanding	28,703,587	21,714,016
Basic and diluted earnings (loss) per share:
Continuing operations	$ (0.38)	$ (0.82)
Discontinued operations		1.12
Basic and diluted earnings (loss) per share	$ (0.38)	$ 0.30