Significant Accounting Policies - Additional Cash Flow Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Accounting Policies [Abstract]
Cash paid for interest	$ 6,666	$ 5,770
Cash paid for income taxes	22,801	25,979
Unsettled purchases of securities	80,586	306,564
Loans foreclosed and transferred to other real estate owned and foreclosed assets	$ 0	$ 422