Other Assets and Intangibles - Components of Other Assets (Parenthetical) (Detail) - Puerto Rico [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Assets [Line Items]
Prepaid tax assets expenses	$ 4.0	$ 16.2	$ 16.8
Aggregate valuation allowance	$ 10.8