Summarized Balance Sheet Information of Reportable Segments (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Current assets:
Cash and cash equivalents	$ 40.2	$ 35.7	$ 38.5
Trade accounts receivable, net	93.7	77.2
Inventories	89.3	101.2
Prepaid expenses, supplies, and other current assets	23.0	24.7
Total current assets	287.4	271.8
Property, plant and equipment, net	290.4	301.5
Intangible assets, net	13.8	15.1
Goodwill	104.5	104.3
Other noncurrent assets	8.0	8.2
TOTAL ASSETS	704.1	700.9
Current liabilities:
Trade payables	112.5	100.9
Accrued liabilities	47.5	51.8
Total current liabilities	162.5	155.1
Accrued pension benefits	38.8	38.0
Environmental liabilities	11.7	11.7
Other noncurrent liabilities	6.2	5.4
TOTAL LIABILITIES	548.6	536.6
Operating Segments | RANA
Current assets:
Cash and cash equivalents	16.4	8.1
Trade accounts receivable, net	77.6	63.7
Inventories	57.3	61.7
Prepaid expenses, supplies, and other current assets	15.7	12.5
Total current assets	167.0	146.0
Property, plant and equipment, net	193.2	199.3
Intangible assets, net	13.8	15.0
Goodwill	95.4	95.4
Other noncurrent assets	5.0	4.9
TOTAL ASSETS	474.4	460.6
Current liabilities:
Trade payables	70.2	58.1
Accrued liabilities	31.3	34.3
Total current liabilities	101.5	92.4
Environmental liabilities	11.7	11.7
Other noncurrent liabilities	4.4	4.1
TOTAL LIABILITIES	117.6	108.2
Operating Segments | RAEU
Current assets:
Cash and cash equivalents	5.3	7.2
Trade accounts receivable, net	16.0	13.5
Financing receivable	40.9	32.7
Inventories	31.1	38.5
Prepaid expenses, supplies, and other current assets	5.9	6.8
Total current assets	99.2	98.7
Property, plant and equipment, net	97.2	102.2
Goodwill	9.1	8.9
Other noncurrent assets	2.0	1.9
TOTAL ASSETS	207.5	211.7
Current liabilities:
Trade payables	42.0	42.3
Accrued liabilities	12.0	14.6
Total current liabilities	54.0	56.9
Accrued pension benefits	38.8	38.0
Other noncurrent liabilities	1.8	1.4
TOTAL LIABILITIES	$ 94.6	$ 96.3