Loans and Leases - Allowance for Loan and Lease Losses by Method of Impairment (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Allowance on loans and leases:
Individually evaluated for impairment	$ 605	$ 462
Collectively evaluated for impairment	20,011	18,964
Allowance on loans and leases	20,616	19,426	$ 17,662	$ 17,525
Carrying value of loans and leases:
Individually evaluated for impairment	23,419	21,377
Collectively evaluated for impairment	3,488,562	3,393,473
Portfolio loans and leases	3,523,514	3,427,154
Purchased credit-impaired
Allowance on loans and leases:
Allowance on loans and leases	0	0
Carrying value of loans and leases:
Portfolio loans and leases	11,533	12,304
Originated
Allowance on loans and leases:
Individually evaluated for impairment	516	365
Collectively evaluated for impairment	20,003	18,964
Allowance on loans and leases	20,519	19,329
Carrying value of loans and leases:
Individually evaluated for impairment	19,554	17,337
Collectively evaluated for impairment	3,012,716	2,867,914
Portfolio loans and leases	3,032,270	2,885,251
Acquired
Carrying value of loans and leases:
Individually evaluated for impairment	3,865	4,040
Collectively evaluated for impairment	475,846	525,559
Portfolio loans and leases	491,244	541,903
Financial Asset Acquired With and Without Credit Deterioration
Allowance on loans and leases:
Individually evaluated for impairment	89	97
Collectively evaluated for impairment	8	0
Allowance on loans and leases	97	97
Commercial mortgage
Allowance on loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	8,241	7,567
Allowance on loans and leases	8,241	7,567	7,174	7,550
Carrying value of loans and leases:
Individually evaluated for impairment	5,558	7,008
Collectively evaluated for impairment	1,731,170	1,642,117
Portfolio loans and leases	1,746,695	1,657,436
Commercial mortgage | Purchased credit-impaired
Allowance on loans and leases:
Allowance on loans and leases	0	0
Carrying value of loans and leases:
Portfolio loans and leases	9,967	8,311
Commercial mortgage | Originated
Allowance on loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	8,241	7,567
Allowance on loans and leases	8,241	7,567
Carrying value of loans and leases:
Individually evaluated for impairment	3,458	4,874
Collectively evaluated for impairment	1,433,153	1,322,948
Portfolio loans and leases	1,436,611	1,327,822
Commercial mortgage | Acquired
Carrying value of loans and leases:
Individually evaluated for impairment	2,100	2,134
Collectively evaluated for impairment	298,017	319,169
Portfolio loans and leases	310,084	329,614
Commercial mortgage | Financial Asset Acquired With and Without Credit Deterioration
Allowance on loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	0	0
Allowance on loans and leases	0	0
Home equity loans and lines
Allowance on loans and leases:
Individually evaluated for impairment	149	162
Collectively evaluated for impairment	889	841
Allowance on loans and leases	1,038	1,003	1,045	1,086
Carrying value of loans and leases:
Individually evaluated for impairment	8,291	4,998
Collectively evaluated for impairment	195,986	201,841
Portfolio loans and leases	204,791	207,351
Home equity loans and lines | Purchased credit-impaired
Allowance on loans and leases:
Allowance on loans and leases	0	0
Carrying value of loans and leases:
Portfolio loans and leases	514	512
Home equity loans and lines | Originated
Allowance on loans and leases:
Individually evaluated for impairment	149	162
Collectively evaluated for impairment	889	841
Allowance on loans and leases	1,038	1,003
Carrying value of loans and leases:
Individually evaluated for impairment	8,265	4,972
Collectively evaluated for impairment	171,810	176,534
Portfolio loans and leases	180,075	181,506
Home equity loans and lines | Acquired
Carrying value of loans and leases:
Individually evaluated for impairment	26	26
Collectively evaluated for impairment	24,176	25,307
Portfolio loans and leases	24,716	25,845
Home equity loans and lines | Financial Asset Acquired With and Without Credit Deterioration
Allowance on loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	0	0
Allowance on loans and leases	0	0
Residential mortgage
Allowance on loans and leases:
Individually evaluated for impairment	259	272
Collectively evaluated for impairment	1,632	1,541
Allowance on loans and leases	1,891	1,813	1,898	1,926
Carrying value of loans and leases:
Individually evaluated for impairment	6,106	6,608
Collectively evaluated for impairment	496,271	487,747
Portfolio loans and leases	502,379	494,355
Residential mortgage | Purchased credit-impaired
Allowance on loans and leases:
Allowance on loans and leases	0	0
Carrying value of loans and leases:
Portfolio loans and leases	2	0
Residential mortgage | Originated
Allowance on loans and leases:
Individually evaluated for impairment	170	175
Collectively evaluated for impairment	1,632	1,541
Allowance on loans and leases	1,802	1,716
Carrying value of loans and leases:
Individually evaluated for impairment	4,719	5,106
Collectively evaluated for impairment	418,919	405,916
Portfolio loans and leases	423,638	411,022
Residential mortgage | Acquired
Carrying value of loans and leases:
Individually evaluated for impairment	1,387	1,502
Collectively evaluated for impairment	77,352	81,831
Portfolio loans and leases	78,741	83,333
Residential mortgage | Financial Asset Acquired With and Without Credit Deterioration
Allowance on loans and leases:
Individually evaluated for impairment	89	97
Collectively evaluated for impairment	0	0
Allowance on loans and leases	89	97
Construction
Allowance on loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	1,186	1,485
Allowance on loans and leases	1,186	1,485	844	937
Carrying value of loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	159,761	178,673
Portfolio loans and leases	159,761	181,078
Construction | Purchased credit-impaired
Allowance on loans and leases:
Allowance on loans and leases	0	0
Carrying value of loans and leases:
Portfolio loans and leases	0	2,405
Construction | Originated
Allowance on loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	1,186	1,485
Allowance on loans and leases	1,186	1,485
Carrying value of loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	157,572	174,592
Portfolio loans and leases	157,572	174,592
Construction | Acquired
Carrying value of loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	2,189	4,081
Portfolio loans and leases	2,189	6,486
Construction | Financial Asset Acquired With and Without Credit Deterioration
Allowance on loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	0	0
Allowance on loans and leases	0	0
Commercial and industrial
Allowance on loans and leases:
Individually evaluated for impairment	160	0
Collectively evaluated for impairment	5,728	5,461
Allowance on loans and leases	5,888	5,461	5,361	5,038
Carrying value of loans and leases:
Individually evaluated for impairment	3,358	2,629
Collectively evaluated for impairment	701,293	691,879
Portfolio loans and leases	705,701	695,584
Commercial and industrial | Purchased credit-impaired
Allowance on loans and leases:
Allowance on loans and leases	0	0
Carrying value of loans and leases:
Portfolio loans and leases	1,050	1,076
Commercial and industrial | Originated
Allowance on loans and leases:
Individually evaluated for impairment	160	0
Collectively evaluated for impairment	5,728	5,461
Allowance on loans and leases	5,888	5,461
Carrying value of loans and leases:
Individually evaluated for impairment	3,050	2,314
Collectively evaluated for impairment	648,154	622,329
Portfolio loans and leases	651,204	624,643
Commercial and industrial | Acquired
Carrying value of loans and leases:
Individually evaluated for impairment	308	315
Collectively evaluated for impairment	53,139	69,550
Portfolio loans and leases	54,497	70,941
Commercial and industrial | Financial Asset Acquired With and Without Credit Deterioration
Allowance on loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	0	0
Allowance on loans and leases	0	0
Consumer
Allowance on loans and leases:
Individually evaluated for impairment	37	28
Collectively evaluated for impairment	291	201
Allowance on loans and leases	328	229	291	246
Carrying value of loans and leases:
Individually evaluated for impairment	106	134
Collectively evaluated for impairment	47,715	46,680
Portfolio loans and leases	47,821	46,814
Consumer | Purchased credit-impaired
Allowance on loans and leases:
Allowance on loans and leases	0	0
Carrying value of loans and leases:
Portfolio loans and leases	0	0
Consumer | Originated
Allowance on loans and leases:
Individually evaluated for impairment	37	28
Collectively evaluated for impairment	291	201
Allowance on loans and leases	328	229
Carrying value of loans and leases:
Individually evaluated for impairment	62	71
Collectively evaluated for impairment	45,167	44,028
Portfolio loans and leases	45,229	44,099
Consumer | Acquired
Carrying value of loans and leases:
Individually evaluated for impairment	44	63
Collectively evaluated for impairment	2,548	2,652
Portfolio loans and leases	2,592	2,715
Consumer | Financial Asset Acquired With and Without Credit Deterioration
Allowance on loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	0	0
Allowance on loans and leases	0	0
Leases
Allowance on loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	2,044	1,868
Allowance on loans and leases	2,044	1,868	1,049	742
Carrying value of loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	156,366	144,536
Portfolio loans and leases	156,366	144,536
Leases | Purchased credit-impaired
Allowance on loans and leases:
Allowance on loans and leases	0	0
Carrying value of loans and leases:
Portfolio loans and leases	0	0
Leases | Originated
Allowance on loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	2,036	1,868
Allowance on loans and leases	2,036	1,868
Carrying value of loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	137,941	121,567
Portfolio loans and leases	137,941	121,567
Leases | Acquired
Carrying value of loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	18,425	22,969
Portfolio loans and leases	18,425	22,969
Leases | Financial Asset Acquired With and Without Credit Deterioration
Allowance on loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	8	0
Allowance on loans and leases	8	0
Unallocated
Allowance on loans and leases:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	0	0
Allowance on loans and leases	0	0	$ 0	$ 0
Unallocated | Purchased credit-impaired
Allowance on loans and leases:
Allowance on loans and leases	$ 0	$ 0