Guarantor Information - Guarantor Condensed Consolidating Balance Sheet Information (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Assets:
Cash and cash equivalents	$ 128.4	$ 258.0	$ 131.4	$ 166.8
Receivables, net of allowance for doubtful accounts	455.0	355.3
Inventories	276.0	280.9
Prepaid expenses and other	100.5	58.9
Current assets of discontinued operations	0.8	36.9
Total current assets	960.7	990.0
Property, plant and equipment, net	1,558.8	1,556.5
Goodwill	856.4	852.1
Customer relationships, net	923.2	950.3
Other intangible assets, net	60.8	63.4
Non-current assets of discontinued operations		62.0
Other assets, net	81.7	65.1
Total assets	4,441.6	4,539.4
Liabilities and Equity:
Current portion of long-term debt	2.5	2.5
Accounts payable	256.3	244.8
Interest payable	15.2	15.4
Income taxes payable	2.4	2.2
Accrued compensation	60.2	41.0
Other accrued liabilities	135.9	94.7
Current liabilities of discontinued operations	6.8	15.5
Total current liabilities	479.3	416.1
Long-term debt, excluding the current portion of long-term debt	1,364.8	1,364.5
Lease financing obligation	46.8	44.0
Deferred income taxes	661.1	683.0
Pension and other post-retirement benefits	189.7	202.8
Non-current liabilities of discontinued operations		35.6
Other non-current liabilities	132.3	140.3
Total liabilities	2,874.0	2,886.3
Equity:
Total Axiall stockholders' equity	1,497.1	1,578.3
Noncontrolling interest	70.5	74.8
Total equity	1,567.6	1,653.1
Total liabilities and equity	4,441.6	4,539.4
Eliminations [Member]
Assets:
Receivables, net of allowance for doubtful accounts	(195.6)	(97.6)
Prepaid expenses and other		(0.4)
Total current assets	(195.6)	(98.0)
Long-term receivables-affiliates	(900.0)	(900.0)
Investment in subsidiaries	(1,644.9)	(1,708.7)
Total assets	(2,740.5)	(2,706.7)
Liabilities and Equity:
Accounts payable	(195.6)	(97.6)
Income taxes payable		(0.4)
Total current liabilities	(195.6)	(98.0)
Long-term payables-affiliates	(900.0)	(900.0)
Other non-current liabilities	(9.5)	(7.2)
Total liabilities	(1,105.1)	(1,005.2)
Equity:
Total Axiall stockholders' equity	(1,635.4)	(1,701.5)
Total equity	(1,635.4)	(1,701.5)
Total liabilities and equity	(2,740.5)	(2,706.7)
Parent Company [Member] | Reportable Legal Entities [Member]
Assets:
Cash and cash equivalents		0.3
Receivables, net of allowance for doubtful accounts	49.4	27.1
Prepaid expenses and other	0.5	0.7
Total current assets	49.9	28.1
Property, plant and equipment, net	10.1	11.0
Long-term receivables-affiliates	900.0	900.0
Other assets, net	4.5	5.6
Investment in subsidiaries	1,177.0	1,235.5
Total assets	2,141.5	2,180.2
Liabilities and Equity:
Accounts payable	127.1	81.7
Interest payable	3.1	3.2
Accrued compensation	1.3	9.5
Other accrued liabilities	34.4	16.2
Total current liabilities	165.9	110.6
Long-term debt, excluding the current portion of long-term debt	444.6	444.2
Deferred income taxes	19.3	18.0
Pension and other post-retirement benefits	3.3	3.6
Other non-current liabilities	11.3	25.5
Total liabilities	644.4	601.9
Equity:
Total Axiall stockholders' equity	1,497.1	1,578.3
Total equity	1,497.1	1,578.3
Total liabilities and equity	2,141.5	2,180.2
Eagle Spinco Inc [Member] | Reportable Legal Entities [Member]
Assets:
Receivables, net of allowance for doubtful accounts	9.1	5.5
Total current assets	9.1	5.5
Other assets, net	1.7	1.7
Investment in subsidiaries	1,795.1	1,833.3
Total assets	1,805.9	1,840.5
Liabilities and Equity:
Accounts payable	49.3	27.0
Interest payable	12.1	12.2
Total current liabilities	61.4	39.2
Long-term debt, excluding the current portion of long-term debt	679.2	678.4
Long-term payables-affiliates	900.0	900.0
Total liabilities	1,640.6	1,617.6
Equity:
Total Axiall stockholders' equity	165.3	222.9
Total equity	165.3	222.9
Total liabilities and equity	1,805.9	1,840.5
Guarantor Subsidiaries Excluding Eagle Spinco Inc [Member] | Reportable Legal Entities [Member]
Assets:
Cash and cash equivalents	24.9	161.7	81.1	78.2
Receivables, net of allowance for doubtful accounts	515.7	377.8
Inventories	218.2	217.6
Prepaid expenses and other	92.1	55.9
Current assets of discontinued operations	0.8	19.3
Total current assets	851.7	832.3
Property, plant and equipment, net	1,380.3	1,357.9
Goodwill	707.8	707.8
Customer relationships, net	795.6	823.1
Other intangible assets, net	60.8	63.1
Non-current assets of discontinued operations		18.4
Other assets, net	73.9	56.2
Investment in subsidiaries	467.9	473.2
Total assets	4,338.0	4,332.0
Liabilities and Equity:
Current portion of long-term debt	2.5	2.5
Accounts payable	236.3	214.9
Income taxes payable		0.4
Accrued compensation	51.6	23.7
Other accrued liabilities	79.6	45.6
Current liabilities of discontinued operations	6.8	9.3
Total current liabilities	376.8	296.4
Long-term debt, excluding the current portion of long-term debt	240.9	241.9
Deferred income taxes	612.1	636.1
Pension and other post-retirement benefits	179.7	189.9
Other non-current liabilities	121.9	113.2
Total liabilities	1,531.4	1,477.5
Equity:
Total Axiall stockholders' equity	2,806.6	2,854.5
Total equity	2,806.6	2,854.5
Total liabilities and equity	4,338.0	4,332.0
Guarantor Subsidiaries Including Eagle Spinco Inc [Member] | Reportable Legal Entities [Member]
Assets:
Cash and cash equivalents	24.9	161.7	81.1	78.2
Receivables, net of allowance for doubtful accounts	515.7	377.8
Inventories	218.2	217.6
Prepaid expenses and other	92.1	55.9
Current assets of discontinued operations	0.8	19.3
Total current assets	851.7	832.3
Property, plant and equipment, net	1,380.3	1,357.9
Goodwill	707.8	707.8
Customer relationships, net	795.6	823.1
Other intangible assets, net	60.8	63.1
Non-current assets of discontinued operations		18.4
Other assets, net	73.9	56.2
Investment in subsidiaries	467.9	473.2
Total assets	4,338.0	4,332.0
Liabilities and Equity:
Current portion of long-term debt	2.5	2.5
Accounts payable	276.5	236.4
Interest payable	12.1	12.2
Income taxes payable		0.4
Accrued compensation	51.6	23.7
Other accrued liabilities	79.6	45.6
Current liabilities of discontinued operations	6.8	9.3
Total current liabilities	429.1	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	610.3	634.4
Pension and other post-retirement benefits	179.7	189.9
Other non-current liabilities	121.9	113.2
Total liabilities	3,161.2	3,087.9
Equity:
Total Axiall stockholders' equity	1,176.8	1,244.1
Total equity	1,176.8	1,244.1
Total liabilities and equity	4,338.0	4,332.0
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Assets:
Cash and cash equivalents	103.5	96.0	$ 50.3	$ 88.6
Receivables, net of allowance for doubtful accounts	85.5	48.0
Inventories	57.8	63.3
Prepaid expenses and other	7.9	2.7
Current assets of discontinued operations		17.6
Total current assets	254.7	227.6
Property, plant and equipment, net	168.4	187.6
Goodwill	148.6	144.3
Customer relationships, net	127.6	127.2
Other intangible assets, net		0.3
Non-current assets of discontinued operations		43.6
Other assets, net	3.3	3.3
Total assets	702.6	733.9
Liabilities and Equity:
Accounts payable	48.3	24.3
Income taxes payable	2.4	2.2
Accrued compensation	7.3	7.8
Other accrued liabilities	21.9	32.9
Current liabilities of discontinued operations		6.2
Total current liabilities	79.9	73.4
Lease financing obligation	46.8	44.0
Deferred income taxes	31.5	30.6
Pension and other post-retirement benefits	6.7	9.3
Non-current liabilities of discontinued operations		35.6
Other non-current liabilities	8.6	8.8
Total liabilities	173.5	201.7
Equity:
Total Axiall stockholders' equity	458.6	457.4
Noncontrolling interest	70.5	74.8
Total equity	529.1	532.2
Total liabilities and equity	$ 702.6	$ 733.9