Loans and Allowance for Loan Losses - Schedule of Accretable Yield of Noncovered PCI Loans, or Income Expected to be Collected (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Accretion of income	$ (11,300)	$ (12,300)
Purchased Credit Impaired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	25,051	27,835	$ 33,603
New loans purchased		2,384	1,556
Accretion of income	(11,308)	(12,252)	(15,217)
Reclassifications from (to) nonaccretable difference	1,941	6,133	7,614
Disposals/other adjustments	591	951	279
Balance at end of period	$ 16,275	$ 25,051	$ 27,835