Significant Accounting Policies - Additional Cash Flow Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Accounting Policies [Abstract]
Cash paid for interest	$ 59,764	$ 15,611
Cash paid for income taxes	5,112	41,969
Unsettled purchases/sales of securities	74,191	41,763
Loans foreclosed and transferred to other real estate owned and foreclosed assets	$ 2,898	$ 257