Premises and Equipment - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Consolidated rental and operating lease expenses	$ 15.1	$ 14.6	$ 12.0
Consolidated premises and equipment depreciation and amortization expenses	$ 42.3	$ 40.7	$ 34.2