Allowance for Loan and Lease Losses and Reserve for Unfunded Commitments - Summary of Recorded Investment, Unpaid Principal Balance, Related Allowance, Average Recorded Investment and Interest Income Recognized (Details) - Loans Excluding Acquired Impaired Loans - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable Impaired [Line Items]
Related Allowance	$ 3,965	$ 1,017	$ 2,326
Recorded Investment	31,111	11,926	8,908
Unpaid Principal Balance	34,479	13,783	11,864
Average Recorded Investment	21,479	12,079	9,055
Interest Income Recognized	1,555	365	212
Commercial Real Estate
Financing Receivable Impaired [Line Items]
Recorded Investment, With no related allowance recorded	11,425	8,916	1,362
Unpaid Principal Balance, With no related allowance recorded	12,936	9,502	1,922
Average Recorded Investment, With no related allowance recorded	10,482	8,975	1,394
Interest Income Recognized, With no related allowance recorded	525	305	64
Recorded Investment, With an allowance recorded	2,459		2,798
Unpaid Principal Balance, With an allowance recorded	2,634		2,797
Related Allowance	1,101		1,076
Average Recorded Investment, With an allowance recorded	1,988		2,826
Interest Income Recognized, With an allowance recorded	187		46
Residential Real Estate
Financing Receivable Impaired [Line Items]
Recorded Investment, With no related allowance recorded	2,075	804	2,821
Unpaid Principal Balance, With no related allowance recorded	2,046	1,999	4,222
Average Recorded Investment, With no related allowance recorded	1,781	827	2,865
Interest Income Recognized, With no related allowance recorded	72	45	63
Recorded Investment, With an allowance recorded	354	496	1,221
Unpaid Principal Balance, With an allowance recorded	351	528	1,216
Related Allowance	158	293	615
Average Recorded Investment, With an allowance recorded	422	519	1,250
Interest Income Recognized, With an allowance recorded	6	1	15
Construction, Land Development, and Other Land
Financing Receivable Impaired [Line Items]
Average Recorded Investment, With no related allowance recorded	295
Interest Income Recognized, With no related allowance recorded	2
Recorded Investment, With an allowance recorded			208
Unpaid Principal Balance, With an allowance recorded			1,201
Related Allowance			137
Average Recorded Investment, With an allowance recorded	14		208
Commercial and Industrial
Financing Receivable Impaired [Line Items]
Recorded Investment, With no related allowance recorded	5,470	521
Unpaid Principal Balance, With no related allowance recorded	6,774	524
Average Recorded Investment, With no related allowance recorded	2,875	516
Interest Income Recognized, With no related allowance recorded	265	(2)
Recorded Investment, With an allowance recorded	9,314	861	171
Unpaid Principal Balance, With an allowance recorded	9,724	869	171
Related Allowance	2,692	396	171
Average Recorded Investment, With an allowance recorded	3,460	914	185
Interest Income Recognized, With an allowance recorded	486		1
Installment and Other
Financing Receivable Impaired [Line Items]
Recorded Investment, With an allowance recorded	14	328	327
Unpaid Principal Balance, With an allowance recorded	14	361	335
Related Allowance	14	328	327
Average Recorded Investment, With an allowance recorded	162	328	327
Interest Income Recognized, With an allowance recorded	$ 12	$ 16	$ 23