Income Taxes - Deferred Taxes - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax [Line Items]
Deferred tax assets, operating loss carryforwards	$ 1.5
Deferred tax assets, valuation allowance	294.8	$ 325.3
Valuation allowance, deferred tax asset, change in amount	35.2	34.3
Valuation allowances and reserves deductions	$ 30.5	$ 17.9
Tax credit carryfoward, expiration range	2020
Deferred tax asset, operating loss carryforwards, foreign (do not expire)	$ 973.0
Deferred tax assets, operating loss carryforwards, subject to expiration	572.0
U.S. Federal NOL's [Member]
Income Tax [Line Items]
Deferred tax assets, operating loss carryforwards	296.0
U.S. Federal NOL's [Member] | NOL Not Utilized in the Current Year [Member]
Income Tax [Line Items]
Deferred tax assets, operating loss carryforwards	289.0
U.S. Federal NOL's [Member] | NOL Utilized in the Current Year [Member]
Income Tax [Line Items]
Deferred tax assets, operating loss carryforwards	$ 31.0
Minimum [Member]
Income Tax [Line Items]
Operating loss carryforwards, expiration date	Jan. 01, 2018
Maximum [Member]
Income Tax [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2037