Unaudited Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information
Revenues	$ 326.3	$ 332.8	$ 350.2	$ 337.1	$ 304.5	$ 314.9	$ 320.9	$ 309.4	$ 1,346.4	$ 1,249.7	$ 1,145.6
Cost of sales	311.0	320.5	332.1	323.7	293.3	298.3	298.6	292.8	1,287.3	1,183.0	1,070.7
Gross profit	15.3	12.3	18.1	13.4	11.2	16.6	22.3	16.6	59.1	66.7	74.9
Operating costs	65.2	47.1	14.3	17.0	78.4	20.1	14.2	18.7
Operating profit (loss)	(49.9)	(34.8)	3.8	(3.6)	(67.2)	(3.5)	8.1	(2.1)	(84.5)	(64.7)	10.2
Net loss attributable to Real Industry, Inc.	(63.0)	(40.8)	(6.5)	(11.4)	(80.4)	(10.9)	(1.5)	(10.1)	(121.7)	(102.9)	(6.9)
Net earnings (loss) available to common stockholders	$ (66.6)	$ (41.6)	$ (7.3)	$ (12.2)	$ (81.2)	$ (11.7)	$ (2.2)	$ (10.8)	$ (127.7)	$ (105.9)	$ (9.2)
Earnings per share - basic and diluted	$ (2.29)	$ (1.43)	$ (0.25)	$ (0.43)	$ (2.84)	$ (0.40)	$ (0.07)	$ (0.38)	$ (4.41)	$ (3.68)	$ (0.35)

Total costs related to goods produced and sold during the reporting period.

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