Allowance for Loan Losses - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Evaluation for impairment of substandard and nonaccrual commercial loans	$ 500,000.0
Impaired fiinancing receivables	$ 60,202,000	$ 45,650,000
Minimum
Financing Receivable, Impaired [Line Items]
Loans considered nonperforming (in days)	90 days
Integrity Bancshares, Inc.
Financing Receivable, Impaired [Line Items]
Acquired loans that experienced credit deterioration since acquisition	$ 21,000,000