Other Operating Expense - (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Income and Expenses [Abstract]
Business Promotion	$ 98.3	$ 95.4	$ 83.6
FDIC Insurance Premiums	27.4	34.7	31.7
Staff Related	33.6	42.8	43.0
Other Intangibles Amortization	17.4	11.4	8.8
Other Expenses	153.9	147.3	197.3
Total Other Operating Expense	$ 330.6	$ 331.6	364.4
Agreement To Settle Securities
Loss Contingencies [Line Items]
Litigation settlement			50.0
Contractual Modifications
Loss Contingencies [Line Items]
Litigation settlement			$ 18.6