Loans - Changes in Carrying Amount of Acquired Loans and Accretable Yield for Loans Receivable (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
FDIC Acquired Loans [Member]
Financing Receivable, Impaired [Line Items]
Carrying Amount of Loans, Balance at beginning of period	$ 252,409	$ 358,666
Carrying Amount of Loans, Payments received, net	(62,579)	(125,388)
Carrying Amount of Loans, Accretion	13,467	19,131
Carrying Amount of Loans, Balance at end of period	203,297	252,409
Accretable Yield, Balance at beginning of period	112,788	122,715
Accretable Yield, Payments received, net	(422)	(1,071)
Accretable Yield, Accretion	(13,467)	(19,131)
Accretable Yield, Decrease in expected cash flows based on actual cash flows and changes in cash flow assumptions	(3,537)	(1,137)
Net transfers from nonaccretable difference to accretable yield	(3,798)	11,412
Accretable Yield, Balance at end of period	91,564	112,788
Acquired Loans [Member]
Financing Receivable, Impaired [Line Items]
Carrying Amount of Loans, Balance at beginning of period	61,276	68,075
Carrying Amount of Loans, Payments received, net	(53,268)	(50,178)
Carrying Amount of Loans, Accretion	14,533	43,379
Carrying Amount of Loans, Balance at end of period	22,541	61,276
Accretable Yield, Balance at beginning of period	74,668	131,370
Accretable Yield, Payments received, net	(21,556)	(32,855)
Accretable Yield, Accretion	(14,533)	(43,379)
Accretable Yield, Decrease in expected cash flows based on actual cash flows and changes in cash flow assumptions	(701)	(203)
Net transfers from nonaccretable difference to accretable yield	46	19,735
Accretable Yield, Balance at end of period	$ 37,924	$ 74,668