Loans and Allowance for Loan Losses - Schedule of Recorded Investment in Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Individually evaluated for impairment	$ 14,033	$ 10,078
Allowance for loan losses, Collectively evaluated for impairment	39,301	40,137
Allowance for loan losses, Loans acquired with deteriorated credit quality	326	166
Total allowance for loan losses	53,660	50,381
Loans and leases outstanding, Individually evaluated for impairment	109,375	92,331
Loans and leases outstanding, Collectively evaluated for impairment	11,146,777	10,982,264
Loans and leases outstanding, Loans acquired with deteriorated credit quality	39,477	43,526
Total loans	11,295,629	11,118,121	$ 9,232,040
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Individually evaluated for impairment	5,871	3,424
Allowance for loan losses, Collectively evaluated for impairment	15,409	15,790
Allowance for loan losses, Loans acquired with deteriorated credit quality	107	32
Total allowance for loan losses	21,387	19,246
Loans and leases outstanding, Individually evaluated for impairment	34,055	26,270
Loans and leases outstanding, Collectively evaluated for impairment	2,924,481	2,685,847
Loans and leases outstanding, Loans acquired with deteriorated credit quality	4,359	5,152
Total loans	2,962,895	2,717,269
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Individually evaluated for impairment	8,162	6,654
Allowance for loan losses, Collectively evaluated for impairment	14,267	14,782
Allowance for loan losses, Loans acquired with deteriorated credit quality	69
Total allowance for loan losses	22,498	21,436
Loans and leases outstanding, Individually evaluated for impairment	75,320	66,061
Loans and leases outstanding, Collectively evaluated for impairment	4,355,891	4,266,665
Loans and leases outstanding, Loans acquired with deteriorated credit quality	20,561	21,826
Total loans	4,451,772	4,354,552
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	1,865	1,763
Allowance for loan losses, Loans acquired with deteriorated credit quality	2
Total allowance for loan losses	1,867	1,763
Loans and leases outstanding, Collectively evaluated for impairment	2,143,658	2,155,750
Loans and leases outstanding, Loans acquired with deteriorated credit quality	10,315	11,303
Total loans	2,153,973	2,167,053
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	7,760	7,802
Allowance for loan losses, Loans acquired with deteriorated credit quality	148	134
Total allowance for loan losses	7,908	7,936
Loans and leases outstanding, Collectively evaluated for impairment	1,722,747	1,874,002
Loans and leases outstanding, Loans acquired with deteriorated credit quality	4,242	5,245
Total loans	$ 1,726,989	$ 1,879,247

Valuation allowance for loans acquired with deteriorated credit quality that are expected to be uncollectible.

No definition available.

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The balance of noncovered loans that were acquired with deteriorated credit quality.

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A valuation allowance for financing receivables that are expected to be uncollectible.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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