Discontinued Operations - Additional Information (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]
Income (loss) from discontinued operations, including tax benefit of $24.5, $4.8, and $0.2, respectively	$ (4.2)	$ (39.4)	$ 3.9
Unrecognized Tax Benefits, Interest on Income Taxes Expense	2.9	5.7	$ (0.8)
Tax Matters Agreement Receivable, Discontinued Operations		$ 13.2
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Tax Matters Agreement Receivable, Discontinued Operations	13.2
Recognition of Previously Unrecognized Tax Position [Member] | Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Tax Adjustments, Settlements, and Unusual Provisions	38.3
Unrecognized Tax Benefits, Interest on Income Taxes Expense	3.2
Tax Expense from Audit Adjustments [Member] | Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Tax Adjustments, Settlements, and Unusual Provisions	$ (17.4)