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Allowance for Loan Losses - Summary of Allowance for Loan Losses and Recorded Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	$ 294		$ 77
Allowance for Loan Losses, Collectively Evaluated for Impairment	60,262		56,313
Total Allowance for Loan Losses	60,556	$ 60,517	56,390	$ 56,712	$ 55,351	$ 52,775
Portfolio Loans, Individually Evaluated for Impairment	30,728		26,823
Portfolio Loans, Collectively Evaluated for Impairment	5,777,079		5,734,626
Total Portfolio Loans	5,807,807		5,761,449
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0		0
Allowance for Loan Losses, Collectively Evaluated for Impairment	32,890		27,235
Total Allowance for Loan Losses	32,890	31,232	27,235	24,975	24,358	19,976
Portfolio Loans, Individually Evaluated for Impairment	3,703		3,546
Portfolio Loans, Collectively Evaluated for Impairment	2,822,669		2,682,448
Total Portfolio Loans			2,685,994
Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0		29
Allowance for Loan Losses, Collectively Evaluated for Impairment	10,226		8,937
Total Allowance for Loan Losses	10,226	10,874	8,966	9,714	9,256	10,810
Portfolio Loans, Individually Evaluated for Impairment	14,548		7,284
Portfolio Loans, Collectively Evaluated for Impairment	1,436,823		1,425,982
Total Portfolio Loans			1,433,266
Commercial construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	268		0
Allowance for Loan Losses, Collectively Evaluated for Impairment	10,647		13,167
Total Allowance for Loan Losses	10,915	11,676	13,167	14,915	13,944	13,999
Portfolio Loans, Individually Evaluated for Impairment	3,298		5,464
Portfolio Loans, Collectively Evaluated for Impairment	280,485		378,870
Total Portfolio Loans			384,334
Consumer real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	10		21
Allowance for Loan Losses, Collectively Evaluated for Impairment	5,028		5,458
Total Allowance for Loan Losses	5,038	5,241	5,479	5,531	5,803	6,095
Portfolio Loans, Individually Evaluated for Impairment	9,157		10,488
Portfolio Loans, Collectively Evaluated for Impairment	1,169,582		1,180,163
Total Portfolio Loans	1,178,739		1,190,651
Other consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	16		27
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,471		1,516
Total Allowance for Loan Losses	1,487	$ 1,494	1,543	$ 1,577	$ 1,990	$ 1,895
Portfolio Loans, Individually Evaluated for Impairment	22		41
Portfolio Loans, Collectively Evaluated for Impairment	$ 67,520		67,163
Total Portfolio Loans			$ 67,204

X

- Definition

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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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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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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