Other Assets, Net - Components of Other Assets (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Other Assets [Line Items]
Amortization expense	$ 18.1		$ 14.4	$ 28.2	$ 47.0
Puerto Rico [Member]
Other Assets [Line Items]
Prepaid tax assets expenses						$ 4.0
Retail Value Inc. [Member]
Other Assets [Line Items]
Wrote-off of prepaid tax assets to other income (expense), net		$ 4.0