Summarized Balance Sheet Information of Reportable Segments (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Current assets:
Cash and cash equivalents	$ 18.4	$ 27.2	$ 40.2
Trade accounts receivable, net	112.9	88.4
Inventories	120.1	118.2
Prepaid expenses, supplies and other current assets	29.0	24.6
Total current assets	312.9	286.8
Property, plant and equipment, net	289.8	289.2
Equity method investment	5.6	5.0
Identifiable intangible assets, net	11.3	12.5
Goodwill	42.9	42.2
Other noncurrent assets	8.5	9.8
TOTAL ASSETS	671.0	645.5
Current liabilities:
Trade payables	124.3	115.8
Accrued liabilities	51.4	46.4
Total current liabilities	178.8	164.5
Accrued pension benefits	45.9	42.0
Environmental liabilities	11.6	11.6
Other noncurrent liabilities	6.7	6.9
TOTAL LIABILITIES	624.0	586.1
Operating Segments | RANA
Current assets:
Cash and cash equivalents	8.7	11.5
Trade accounts receivable, net	96.4	76.2
Financing receivable	0.0	0.0
Inventories	83.1	79.3
Prepaid expenses, supplies and other current assets	19.3	13.7
Total current assets	207.5	180.7
Property, plant and equipment, net	187.8	195.0
Equity method investment	5.6	5.0
Identifiable intangible assets, net	11.3	12.5
Goodwill	33.6	33.6
Other noncurrent assets	3.8	5.0
TOTAL ASSETS	449.6	431.8
Current liabilities:
Trade payables	80.4	73.8
Accrued liabilities	33.0	30.0
Total current liabilities	113.4	103.8
Accrued pension benefits	0.0	0.0
Environmental liabilities	11.6	11.6
Other noncurrent liabilities	4.7	4.5
TOTAL LIABILITIES	129.7	119.9
Operating Segments | RAEU
Current assets:
Cash and cash equivalents	5.3	5.7
Trade accounts receivable, net	16.5	12.2
Financing receivable	32.5	28.4
Inventories	37.0	38.9
Prepaid expenses, supplies and other current assets	7.2	6.4
Total current assets	98.5	91.6
Property, plant and equipment, net	102.0	94.2
Equity method investment	0.0	0.0
Identifiable intangible assets, net	0.0	0.0
Goodwill	9.3	8.6
Other noncurrent assets	3.8	3.5
TOTAL ASSETS	213.6	197.9
Current liabilities:
Trade payables	43.9	41.8
Accrued liabilities	15.3	13.4
Total current liabilities	59.2	55.2
Accrued pension benefits	45.9	42.0
Environmental liabilities	0.0	0.0
Other noncurrent liabilities	1.9	1.8
TOTAL LIABILITIES	$ 107.0	$ 99.0