Premises and Equipment, Net - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Depreciation and amortization for premises and equipment	$ 47.5	$ 49.7	$ 53.8
Amortization expense for computer software	37.4	37.9	$ 40.7
Unamortized computer software costs	$ 62.7	$ 70.4