Allowance for Loan Losses and Reserve for Unfunded Loan Commitments - Activity in Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	$ 14,634	$ 12,800	$ 13,556	$ 12,579
Charge-offs	(169)	(240)	(376)	(778)
Recoveries	23	53	258	162
Net (charge-offs) recoveries	(146)	(187)	(118)	(616)
Provision (credit) for loan losses charged to expense	500	500	1,550	1,150
Ending Balance	14,988	13,113	14,988	13,113
SBA loans held for investment
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,637	1,514	1,471	1,576
Charge-offs	(169)	(34)	(354)	(293)
Recoveries	1	36	68	76
Net (charge-offs) recoveries	(168)	2	(286)	(217)
Provision (credit) for loan losses charged to expense	66	108	350	265
Ending Balance	1,535	1,624	1,535	1,624
Commercial loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	8,355	7,387	7,825	7,302
Charge-offs	0	(31)	0	(227)
Recoveries	5	15	25	71
Net (charge-offs) recoveries	5	(16)	25	(156)
Provision (credit) for loan losses charged to expense	317	83	827	308
Ending Balance	8,677	7,454	8,677	7,454
Residential mortgage loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	3,493	2,816	3,130	2,593
Charge-offs	0	(5)	0	(5)
Recoveries	0	0	13	12
Net (charge-offs) recoveries	0	(5)	13	7
Provision (credit) for loan losses charged to expense	119	83	469	294
Ending Balance	3,612	2,894	3,612	2,894
Consumer loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,149	1,083	1,130	925
Charge-offs	0	(170)	(22)	(253)
Recoveries	17	2	152	3
Net (charge-offs) recoveries	17	(168)	130	(250)
Provision (credit) for loan losses charged to expense	(2)	226	(96)	466
Ending Balance	1,164	1,141	1,164	1,141
Unallocated
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	0	0	0	183
Charge-offs		0		0
Recoveries		0		0
Net (charge-offs) recoveries	0	0	0	0
Provision (credit) for loan losses charged to expense	0	0	0	(183)
Ending Balance	$ 0	$ 0	$ 0	$ 0

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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- Definition

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

+ References

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- Definition

Amount, after recoveries, of loans and leases that have been written-off.

+ References

No definition available.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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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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- Definition

Amount of expense related to estimated loss from loan and lease transactions.

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