Accumulated Other Comprehensive Income (Loss) and Other Comprehensive Income (Loss) - Schedule of Amounts Recorded in Accumulated Other Comprehensive Loss, Net of Tax, and Changes within the Period (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	$ 1,653.1
Other comprehensive income (loss) attributable to Axiall, net of tax	21.9	$ (27.8)
Balance at the end of the period	1,611.9
Change in Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(89.4)
Other comprehensive income before reclassifications	23.4
Other comprehensive income (loss) attributable to Axiall, net of tax	23.4
Balance at the end of the period	(66.0)
Change in Derivative Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	0.5
Other comprehensive income before reclassifications	0.1
Amounts reclassified from accumulated other comprehensive loss, net of tax	(0.2)
Other comprehensive income (loss) attributable to Axiall, net of tax	(0.1)
Balance at the end of the period	0.4
Change in Pension and OPEB Liability Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(29.1)
Other comprehensive income before reclassifications	0.1
Amounts reclassified from accumulated other comprehensive loss, net of tax	(1.5)
Other comprehensive income (loss) attributable to Axiall, net of tax	(1.4)
Balance at the end of the period	(30.5)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(118.0)
Other comprehensive income before reclassifications	23.6
Amounts reclassified from accumulated other comprehensive loss, net of tax	(1.7)
Other comprehensive income (loss) attributable to Axiall, net of tax	21.9
Balance at the end of the period	$ (96.1)

Accumulated Other Comprehensive Income (Loss) and Other Comprehensive Income (Loss) - Schedule of Amounts Recorded in Accumulated Other Comprehensive Loss, Net of Tax, and Changes within the Period (Detail) - USD ($)
$ in Millions

3 Months Ended

Mar. 31, 2016

Mar. 31, 2015

Accumulated Other Comprehensive Income (Loss) [Line Items]

Balance at the beginning of the period

$ 1,653.1

Other comprehensive income (loss) attributable to Axiall, net of tax

21.9

$ (27.8)

Balance at the end of the period

1,611.9

Change in Foreign Currency Translation Adjustment [Member]