Significant Accounting Policies - Additional Cash Flow Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Accounting Policies [Abstract]
Cash paid for interest	$ 9,906	$ 10,519
Cash paid for income taxes	35,300	45,186
Unsettled security transactions	3,428	61,974
Loans foreclosed and transferred to other real estate owned and foreclosed assets	826	1,993
Premises and equipment transferred to other real estate owned and foreclosed assets	0	1,799
Loans to facilitate the sale of other real estate owned	$ 20	$ 102