Summarized Balance Sheet Information of Reportable Segments (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Current assets:
Cash and cash equivalents	$ 34.6	$ 35.7	$ 44.9
Trade accounts receivable, net	97.1	77.2
Inventories	95.5	101.2
Prepaid expenses, supplies, and other current assets	25.9	24.7
Total current assets	298.3	271.8
Property, plant and equipment, net	287.3	301.5
Intangible assets, net	13.2	15.1
Goodwill	104.6	104.3
Other noncurrent assets	8.9	8.2
TOTAL ASSETS	712.3	700.9
Current liabilities:
Trade payables	112.4	100.9
Accrued liabilities	41.6	51.8
Total current liabilities	156.5	155.1
Accrued pension benefits	39.3	38.0
Environmental liabilities	11.7	11.7
Other noncurrent liabilities	6.9	5.4
TOTAL LIABILITIES	565.0	536.6
Operating Segments | RANA
Current assets:
Cash and cash equivalents	15.8	8.1
Trade accounts receivable, net	80.9	63.7
Financing receivable	0.0	0.0
Inventories	65.0	61.7
Prepaid expenses, supplies, and other current assets	15.5	12.5
Total current assets	177.2	146.0
Property, plant and equipment, net	189.8	199.3
Intangible assets, net	13.2	15.0
Goodwill	95.4	95.4
Other noncurrent assets	5.0	4.9
TOTAL ASSETS	480.6	460.6
Current liabilities:
Trade payables	70.8	58.1
Accrued liabilities	22.2	34.3
Total current liabilities	93.0	92.4
Accrued pension benefits	0.0	0.0
Environmental liabilities	11.7	11.7
Other noncurrent liabilities	4.5	4.1
TOTAL LIABILITIES	109.2	108.2
Operating Segments | RAEU
Current assets:
Cash and cash equivalents	5.8	7.2
Trade accounts receivable, net	16.2	13.5
Financing receivable	45.2	32.7
Inventories	29.7	38.5
Prepaid expenses, supplies, and other current assets	6.9	6.8
Total current assets	103.8	98.7
Property, plant and equipment, net	97.4	102.2
Intangible assets, net	0.0	0.0
Goodwill	9.2	8.9
Other noncurrent assets	2.8	1.9
TOTAL ASSETS	213.2	211.7
Current liabilities:
Trade payables	41.4	42.3
Accrued liabilities	14.1	14.6
Total current liabilities	55.5	56.9
Accrued pension benefits	39.3	38.0
Environmental liabilities	0.0	0.0
Other noncurrent liabilities	1.8	1.4
TOTAL LIABILITIES	$ 96.6	$ 96.3