Other Assets and Accounts Payable, Accrued Expenses and Other Liabilities - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Other Assets [Line Items]
Depreciation expense	$ 23.9	$ 25.2	$ 32.0
Accounts Payable, Accrued Expenses and Other Liabilities for redemption to investors	15.6	27.2
Payables relating to unsettled purchases	$ 311.4	$ 1.5