Loss Per Share - Reconciliation of Numerators and Denominators Used for Basic and Diluted Loss Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Numerator
Loss from continuing operations	$ (30.3)	$ (2.4)
Less: net income attributable to noncontrolling interest	0.3	1.8
Loss from continuing operations attributable to Axiall	(30.6)	(4.2)
Net loss from discontinued operations	(23.0)	(6.4)
Consolidated net loss attributable to Axiall	$ (53.6)	$ (10.6)
Denominator
Weighted average common shares outstanding, basic	70.6	70.2
Dilutive impact of stock options and other share-based awards	0.0	0.0
Weighted average common shares outstanding, diluted	70.6	70.2
Basic loss per share attributable to Axiall:
Basic loss per share from continuing operations	$ (0.43)	$ (0.06)
Basic loss per share from discontinued operations	(0.33)	(0.09)
Basic loss per share attributable to Axiall	(0.76)	(0.15)
Diluted loss per share attributable to Axiall:
Diluted loss per share from continuing operations	(0.43)	(0.06)
Diluted loss per share from discontinued operations	(0.33)	(0.09)
Diluted loss per share attributable to Axiall	$ (0.76)	$ (0.15)