Statements of Operations of Discontinued Operations (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Revenues		$ 0.7	$ 39.8
Cost of sales		0.4	25.3
Gross profit		0.3	14.5
Selling, general and administrative expenses	$ 0.3	0.5	6.5
Other operating expense, net	6.0	2.5	0.4
Operating profit (loss)	(0.3)	(0.2)	6.9
Nonoperating income, net	(39.1)	(51.0)	(0.1)
Earnings before income taxes	0.9	44.5	9.2
Income tax expense	0.3	19.6	3.7
Earnings from discontinued operations, net of income taxes	0.6	24.9	5.5
Discontinued Operations
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Other operating expense, net			1.1
Nonoperating income, net	$ 1.2	$ 44.7	$ 2.3