Guarantor Information - Guarantor Condensed Consolidating Balance Sheet Information (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Assets:
Cash and cash equivalents	$ 201.4	$ 258.0	$ 134.7	$ 166.8
Receivables, net of allowance for doubtful accounts	381.2	355.3
Inventories	307.2	280.9
Prepaid expenses and other	69.1	58.9
Current assets of discontinued operations	0.6	36.9
Total current assets	959.5	990.0
Property, plant and equipment, net	1,539.8	1,556.5
Goodwill	856.2	852.1
Customer relationships, net	938.9	950.3
Other intangible assets, net	62.0	63.4
Non-current assets of discontinued operations		62.0
Other assets, net	70.1	65.1
Total assets	4,426.5	4,539.4
Liabilities and Equity:
Current portion of long-term debt	2.5	2.5
Accounts payable	260.3	244.8
Interest payable	12.8	15.4
Income taxes payable	2.3	2.2
Accrued compensation	38.0	41.0
Other accrued liabilities	84.4	94.7
Current liabilities of discontinued operations	5.5	15.5
Total current liabilities	405.8	416.1
Long-term debt, excluding the current portion of long-term debt	1,364.6	1,364.5
Lease financing obligation	46.9	44.0
Deferred income taxes	678.7	683.0
Pension and other post-retirement benefits	193.8	202.8
Non-current liabilities of discontinued operations		35.6
Other non-current liabilities	124.8	140.3
Total liabilities	2,814.6	2,886.3
Equity:
Total Axiall stockholders' equity	1,534.9	1,578.3
Noncontrolling interest	77.0	74.8
Total equity	1,611.9	1,653.1
Total liabilities and equity	4,426.5	4,539.4
Eliminations [Member]
Assets:
Receivables, net of allowance for doubtful accounts	(156.1)	(97.6)
Prepaid expenses and other		(0.4)
Total current assets	(156.1)	(98.0)
Long-term receivables-affiliates	(900.0)	(900.0)
Investment in subsidiaries	(1,673.9)	(1,708.7)
Total assets	(2,730.0)	(2,706.7)
Liabilities and Equity:
Accounts payable	(156.1)	(97.6)
Income taxes payable		(0.4)
Total current liabilities	(156.1)	(98.0)
Long-term payables-affiliates	(900.0)	(900.0)
Other non-current liabilities	(10.7)	(7.2)
Total liabilities	(1,066.8)	(1,005.2)
Equity:
Total Axiall stockholders' equity	(1,663.2)	(1,701.5)
Total equity	(1,663.2)	(1,701.5)
Total liabilities and equity	(2,730.0)	(2,706.7)
Parent Company [Member] | Reportable Legal Entities [Member]
Assets:
Cash and cash equivalents	0.5	0.3
Receivables, net of allowance for doubtful accounts	38.6	27.1
Prepaid expenses and other	0.4	0.7
Total current assets	39.5	28.1
Property, plant and equipment, net	10.7	11.0
Long-term receivables-affiliates	900.0	900.0
Other assets, net	4.9	5.6
Investment in subsidiaries	1,207.1	1,235.5
Total assets	2,162.2	2,180.2
Liabilities and Equity:
Accounts payable	123.6	81.7
Interest payable	8.6	3.2
Accrued compensation	1.9	9.5
Other accrued liabilities	15.3	16.2
Total current liabilities	149.4	110.6
Long-term debt, excluding the current portion of long-term debt	444.4	444.2
Deferred income taxes	19.2	18.0
Pension and other post-retirement benefits	3.3	3.6
Other non-current liabilities	11.0	25.5
Total liabilities	627.3	601.9
Equity:
Total Axiall stockholders' equity	1,534.9	1,578.3
Total equity	1,534.9	1,578.3
Total liabilities and equity	2,162.2	2,180.2
Eagle Spinco Inc [Member] | Reportable Legal Entities [Member]
Assets:
Receivables, net of allowance for doubtful accounts	0.6	5.5
Total current assets	0.6	5.5
Other assets, net	1.7	1.7
Investment in subsidiaries	1,827.5	1,833.3
Total assets	1,829.8	1,840.5
Liabilities and Equity:
Accounts payable	38.5	27.0
Interest payable	4.2	12.2
Total current liabilities	42.7	39.2
Long-term debt, excluding the current portion of long-term debt	678.8	678.4
Long-term payables-affiliates	900.0	900.0
Total liabilities	1,621.5	1,617.6
Equity:
Total Axiall stockholders' equity	208.3	222.9
Total equity	208.3	222.9
Total liabilities and equity	1,829.8	1,840.5
Guarantor Subsidiaries Excluding Eagle Spinco Inc [Member] | Reportable Legal Entities [Member]
Assets:
Cash and cash equivalents	80.6	161.7	76.3	78.2
Receivables, net of allowance for doubtful accounts	436.3	377.8
Inventories	246.2	217.6
Prepaid expenses and other	62.6	55.9
Current assets of discontinued operations	0.6	19.3
Total current assets	826.3	832.3
Property, plant and equipment, net	1,359.7	1,357.9
Goodwill	707.8	707.8
Customer relationships, net	809.4	823.1
Other intangible assets, net	62.0	63.1
Non-current assets of discontinued operations		18.4
Other assets, net	61.8	56.2
Investment in subsidiaries	466.8	473.2
Total assets	4,293.8	4,332.0
Liabilities and Equity:
Current portion of long-term debt	2.5	2.5
Accounts payable	222.9	214.9
Income taxes payable		0.4
Accrued compensation	28.2	23.7
Other accrued liabilities	37.7	45.6
Current liabilities of discontinued operations	5.5	9.3
Total current liabilities	296.8	296.4
Long-term debt, excluding the current portion of long-term debt	241.3	241.9
Deferred income taxes	629.6	636.1
Pension and other post-retirement benefits	184.0	189.9
Other non-current liabilities	116.0	113.2
Total liabilities	1,467.7	1,477.5
Equity:
Total Axiall stockholders' equity	2,826.1	2,854.5
Total equity	2,826.1	2,854.5
Total liabilities and equity	4,293.8	4,332.0
Guarantor Subsidiaries Including Eagle Spinco Inc [Member] | Reportable Legal Entities [Member]
Assets:
Cash and cash equivalents	80.6	161.7	76.3	78.2
Receivables, net of allowance for doubtful accounts	436.3	377.8
Inventories	246.2	217.6
Prepaid expenses and other	62.6	55.9
Current assets of discontinued operations	0.6	19.3
Total current assets	826.3	832.3
Property, plant and equipment, net	1,359.7	1,357.9
Goodwill	707.8	707.8
Customer relationships, net	809.4	823.1
Other intangible assets, net	62.0	63.1
Non-current assets of discontinued operations		18.4
Other assets, net	61.8	56.2
Investment in subsidiaries	466.8	473.2
Total assets	4,293.8	4,332.0
Liabilities and Equity:
Current portion of long-term debt	2.5	2.5
Accounts payable	260.7	236.4
Interest payable	4.2	12.2
Income taxes payable		0.4
Accrued compensation	28.2	23.7
Other accrued liabilities	37.7	45.6
Current liabilities of discontinued operations	5.5	9.3
Total current liabilities	338.8	330.1
Long-term debt, excluding the current portion of long-term debt	920.2	920.3
Long-term payables-affiliates	900.0	900.0
Deferred income taxes	627.9	634.4
Pension and other post-retirement benefits	184.0	189.9
Other non-current liabilities	116.0	113.2
Total liabilities	3,086.9	3,087.9
Equity:
Total Axiall stockholders' equity	1,206.9	1,244.1
Total equity	1,206.9	1,244.1
Total liabilities and equity	4,293.8	4,332.0
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Assets:
Cash and cash equivalents	120.3	96.0	$ 58.4	$ 88.6
Receivables, net of allowance for doubtful accounts	62.4	48.0
Inventories	61.0	63.3
Prepaid expenses and other	6.1	2.7
Current assets of discontinued operations		17.6
Total current assets	249.8	227.6
Property, plant and equipment, net	169.4	187.6
Goodwill	148.4	144.3
Customer relationships, net	129.5	127.2
Other intangible assets, net		0.3
Non-current assets of discontinued operations		43.6
Other assets, net	3.4	3.3
Total assets	700.5	733.9
Liabilities and Equity:
Accounts payable	32.1	24.3
Income taxes payable	2.3	2.2
Accrued compensation	7.9	7.8
Other accrued liabilities	31.4	32.9
Current liabilities of discontinued operations		6.2
Total current liabilities	73.7	73.4
Lease financing obligation	46.9	44.0
Deferred income taxes	31.6	30.6
Pension and other post-retirement benefits	6.5	9.3
Non-current liabilities of discontinued operations		35.6
Other non-current liabilities	8.5	8.8
Total liabilities	167.2	201.7
Equity:
Total Axiall stockholders' equity	456.3	457.4
Noncontrolling interest	77.0	74.8
Total equity	533.3	532.2
Total liabilities and equity	$ 700.5	$ 733.9