Summarized Balance Sheet Information of Reportable Segments (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Current assets:
Cash and cash equivalents	$ 37.0	$ 35.7	$ 28.6
Trade accounts receivable, net	89.1	77.2
Inventories	94.9	101.2
Prepaid expenses, supplies, and other current assets	23.5	24.7
Total current assets	279.9	271.8
Property, plant and equipment, net	296.2	301.5
Intangible assets, net	14.5	15.1
Goodwill	105.0	104.3
Other noncurrent assets	8.1	8.2
TOTAL ASSETS	703.7	700.9
Current liabilities:
Trade payables	102.4	100.9
Accrued liabilities	43.8	51.8
Total current liabilities	148.7	155.1
Accrued pension benefits	39.7	38.0
Environmental liabilities	11.7	11.7
Other noncurrent liabilities	6.0	5.4
TOTAL LIABILITIES	546.3	536.6
RANA
Current assets:
Cash and cash equivalents	11.1	8.1
Trade accounts receivable, net	72.1	63.7
Inventories	61.4	61.7
Prepaid expenses, supplies, and other current assets	14.8	12.5
Total current assets	159.4	146.0
Property, plant and equipment, net	196.4	199.3
Intangible assets, net	14.4	15.0
Goodwill	95.7	95.4
Other noncurrent assets	4.9	4.9
TOTAL ASSETS	470.8	460.6
Current liabilities:
Trade payables	65.9	58.1
Accrued liabilities	24.6	34.3
Total current liabilities	90.5	92.4
Environmental liabilities	11.7	11.7
Other noncurrent liabilities	4.2	4.1
TOTAL LIABILITIES	106.4	108.2
RAEU
Current assets:
Cash and cash equivalents	5.4	7.2
Trade accounts receivable, net	17.0	13.5
Financing receivable	35.3	32.7
Inventories	32.5	38.5
Prepaid expenses, supplies, and other current assets	7.2	6.8
Total current assets	97.4	98.7
Property, plant and equipment, net	99.8	102.2
Goodwill	9.3	8.9
Other noncurrent assets	2.0	1.9
TOTAL ASSETS	208.5	211.7
Current liabilities:
Trade payables	36.3	42.3
Accrued liabilities	15.6	14.6
Total current liabilities	51.9	56.9
Accrued pension benefits	39.7	38.0
Other noncurrent liabilities	2.0	1.4
TOTAL LIABILITIES	$ 93.6	$ 96.3