Summary of Significant Accounting Policies (Additional Cash Flow Information) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Cash paid for interest	$ 11,886	$ 12,982	$ 14,705
Cash paid for income tax	50,427	57,086	62,976
Deferred gain on sale of building and parking garage	7,099	0	0
Unsettled purchases of securities	0	2,998	0
Loans foreclosed and transferred to other real estate owned and foreclosed assets	0	933	4,363
Premises and equipment transferred to other real estate owned and foreclosed assets	0	0	1,740
Loans to facilitate the sale of other real estate owned	$ 753	$ 20	$ 102