Summarized Balance Sheet Information of Reportable Segments (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Current assets:
Cash and cash equivalents	$ 18.5	$ 27.2	$ 37.0
Trade accounts receivable, net	113.9	88.4
Inventories	111.8	118.2
Prepaid expenses, supplies and other current assets	29.9	24.6
Total current assets	306.6	286.8
Property, plant and equipment, net	287.2	289.2
Equity method investment	6.1	5.0
Identifiable intangible assets, net	11.9	12.5
Goodwill	42.3	42.2
Other noncurrent assets	9.5	9.8
TOTAL ASSETS	663.6	645.5
Current liabilities:
Trade payables	129.4	115.8
Accrued liabilities	40.4	46.4
Total current liabilities	172.7	164.5
Accrued pension benefits	42.8	42.0
Environmental liabilities	11.6	11.6
Other noncurrent liabilities	6.8	6.9
TOTAL LIABILITIES	615.6	586.1
Operating Segments | RANA
Current assets:
Cash and cash equivalents	7.4	11.5
Trade accounts receivable, net	96.1	76.2
Financing receivable	0.0	0.0
Inventories	74.9	79.3
Prepaid expenses, supplies and other current assets	19.6	13.7
Total current assets	198.0	180.7
Property, plant and equipment, net	190.6	195.0
Equity method investment	6.1	5.0
Identifiable intangible assets, net	11.9	12.5
Goodwill	33.5	33.6
Other noncurrent assets	4.9	5.0
TOTAL ASSETS	445.0	431.8
Current liabilities:
Trade payables	84.2	73.8
Accrued liabilities	20.6	30.0
Total current liabilities	104.8	103.8
Accrued pension benefits	0.0	0.0
Environmental liabilities	11.6	11.6
Other noncurrent liabilities	4.6	4.5
TOTAL LIABILITIES	121.0	119.9
Operating Segments | RAEU
Current assets:
Cash and cash equivalents	4.4	5.7
Trade accounts receivable, net	17.8	12.2
Financing receivable	32.5	28.4
Inventories	36.9	38.9
Prepaid expenses, supplies and other current assets	6.6	6.4
Total current assets	98.2	91.6
Property, plant and equipment, net	96.6	94.2
Equity method investment	0.0	0.0
Identifiable intangible assets, net	0.0	0.0
Goodwill	8.8	8.6
Other noncurrent assets	3.6	3.5
TOTAL ASSETS	207.2	197.9
Current liabilities:
Trade payables	45.2	41.8
Accrued liabilities	16.2	13.4
Total current liabilities	61.4	55.2
Accrued pension benefits	42.8	42.0
Environmental liabilities	0.0	0.0
Other noncurrent liabilities	1.8	1.8
TOTAL LIABILITIES	$ 106.0	$ 99.0