Discontinued Operations - Statements of Operations of Discontinued Operations (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Discontinued operations
Revenues			$ 0.7
Cost of sales			0.4
Gross profit			0.3
Selling, general and administrative expenses	$ 0.2	$ 0.3	0.5
Operating profit (loss)	(0.2)	(0.3)	(0.2)
Nonoperating income, net	0.2	1.2	44.7
Earnings before income taxes		0.9	44.5
Income tax expense		0.3	19.6
Earnings (loss) from discontinued operations, net of income taxes		$ 0.6	$ 24.9
Discontinued Operations
Discontinued operations
Earnings (loss) from discontinued operations, net of income taxes	$ 0.0