Loans and Leases - Past Due Loans and Leases (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	$ 10,379	$ 7,959
Loans and leases, current	3,369,674	3,269,320
Loans and leases, accruing	3,380,053	3,277,279
Non-accrual loans and leases	9,448	8,579
Total portfolio loans and leases	3,389,501	3,285,858
Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	8,415	3,081
Loans and leases, current	2,687,365	2,480,470
Loans and leases, accruing	2,695,780	2,483,551
Non-accrual loans and leases	5,034	3,745
Total portfolio loans and leases	2,700,814	2,487,296
Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	1,964	4,878
Loans and leases, current	682,309	788,850
Loans and leases, accruing	684,273	793,728
Non-accrual loans and leases	4,414	4,834
Total portfolio loans and leases	688,687	798,562
Administratively Delinquent
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, current	6,200	4,100
Commercial mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	2,795	3,794
Loans and leases, current	1,609,915	1,518,711
Loans and leases, accruing	1,612,710	1,522,505
Non-accrual loans and leases	1,011	872
Total portfolio loans and leases	1,613,721	1,523,377
Commercial mortgage | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	2,184	1,336
Loans and leases, current	1,235,701	1,120,901
Loans and leases, accruing	1,237,885	1,122,237
Non-accrual loans and leases	0	90
Total portfolio loans and leases	1,237,885	1,122,327
Commercial mortgage | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	611	2,458
Loans and leases, current	374,214	397,810
Loans and leases, accruing	374,825	400,268
Non-accrual loans and leases	1,011	782
Total portfolio loans and leases	375,836	401,050
Home equity loans and lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	348
Loans and leases, current	204,106	216,446
Loans and leases, accruing	204,106	216,794
Non-accrual loans and leases	2,323	1,481
Total portfolio loans and leases	206,429	218,275
Home equity loans and lines | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	26
Loans and leases, current	174,938	182,036
Loans and leases, accruing	174,938	182,062
Non-accrual loans and leases	1,833	1,221
Total portfolio loans and leases	176,771	183,283
Home equity loans and lines | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	322
Loans and leases, current	29,168	34,410
Loans and leases, accruing	29,168	34,732
Non-accrual loans and leases	490	260
Total portfolio loans and leases	29,658	34,992
Residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	1,018	1,465
Loans and leases, current	445,395	453,004
Loans and leases, accruing	446,413	454,469
Non-accrual loans and leases	2,647	4,417
Total portfolio loans and leases	449,060	458,886
Residential mortgage | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	690	721
Loans and leases, current	355,966	358,709
Loans and leases, accruing	356,656	359,430
Non-accrual loans and leases	1,615	1,505
Total portfolio loans and leases	358,271	360,935
Residential mortgage | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	328	744
Loans and leases, current	89,429	94,295
Loans and leases, accruing	89,757	95,039
Non-accrual loans and leases	1,032	2,912
Total portfolio loans and leases	90,789	97,951
Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	3,937	0
Loans and leases, current	186,937	212,454
Loans and leases, accruing	190,874	212,454
Non-accrual loans and leases	0	0
Total portfolio loans and leases	190,874	212,454
Construction | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	3,937	0
Loans and leases, current	143,699	128,266
Loans and leases, accruing	147,636	128,266
Non-accrual loans and leases	0	0
Total portfolio loans and leases	147,636	128,266
Construction | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Loans and leases, current	43,238	84,188
Loans and leases, accruing	43,238	84,188
Non-accrual loans and leases	0	0
Total portfolio loans and leases	43,238	84,188
Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	995	944
Loans and leases, current	742,726	716,662
Loans and leases, accruing	743,721	717,606
Non-accrual loans and leases	1,585	1,706
Total portfolio loans and leases	745,306	719,312
Commercial and industrial | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	766	675
Loans and leases, current	631,140	587,803
Loans and leases, accruing	631,906	588,478
Non-accrual loans and leases	1,011	826
Total portfolio loans and leases	632,917	589,304
Commercial and industrial | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	229	269
Loans and leases, current	111,586	128,859
Loans and leases, accruing	111,815	129,128
Non-accrual loans and leases	574	880
Total portfolio loans and leases	112,389	130,008
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	19	1,106
Loans and leases, current	51,443	37,047
Loans and leases, accruing	51,462	38,153
Non-accrual loans and leases	0	0
Total portfolio loans and leases	51,462	38,153
Consumer | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	19	21
Loans and leases, current	49,809	35,125
Loans and leases, accruing	49,828	35,146
Non-accrual loans and leases	0	0
Total portfolio loans and leases	49,828	35,146
Consumer | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	1,085
Loans and leases, current	1,634	1,922
Loans and leases, accruing	1,634	3,007
Non-accrual loans and leases	0	0
Total portfolio loans and leases	1,634	3,007
Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	1,615	302
Loans and leases, current	129,152	114,996
Loans and leases, accruing	130,767	115,298
Non-accrual loans and leases	1,882	103
Total portfolio loans and leases	132,649	115,401
Leases | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	819	302
Loans and leases, current	96,112	67,630
Loans and leases, accruing	96,931	67,932
Non-accrual loans and leases	575	103
Total portfolio loans and leases	97,506	68,035
Leases | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	796	0
Loans and leases, current	33,040	47,366
Loans and leases, accruing	33,836	47,366
Non-accrual loans and leases	1,307	0
Total portfolio loans and leases	35,143	47,366
30 – 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	8,027	4,979
30 – 59 Days Past Due | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	6,683	2,587
30 – 59 Days Past Due | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	1,344	2,392
30 – 59 Days Past Due | Commercial mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	2,645	1,366
30 – 59 Days Past Due | Commercial mortgage | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	2,107	1,255
30 – 59 Days Past Due | Commercial mortgage | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	538	111
30 – 59 Days Past Due | Home equity loans and lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	338
30 – 59 Days Past Due | Home equity loans and lines | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	26
30 – 59 Days Past Due | Home equity loans and lines | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	312
30 – 59 Days Past Due | Residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	891	1,386
30 – 59 Days Past Due | Residential mortgage | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	626	721
30 – 59 Days Past Due | Residential mortgage | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	265	665
30 – 59 Days Past Due | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	2,854	0
30 – 59 Days Past Due | Construction | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	2,854	0
30 – 59 Days Past Due | Construction | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
30 – 59 Days Past Due | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	832	658
30 – 59 Days Past Due | Commercial and industrial | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	766	439
30 – 59 Days Past Due | Commercial and industrial | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	66	219
30 – 59 Days Past Due | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	19	1,106
30 – 59 Days Past Due | Consumer | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	19	21
30 – 59 Days Past Due | Consumer | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	1,085
30 – 59 Days Past Due | Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	786	125
30 – 59 Days Past Due | Leases | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	311	125
30 – 59 Days Past Due | Leases | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	475	0
60 – 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	2,352	2,980
60 – 89 Days Past Due | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	1,732	494
60 – 89 Days Past Due | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	620	2,486
60 – 89 Days Past Due | Commercial mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	150	2,428
60 – 89 Days Past Due | Commercial mortgage | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	77	81
60 – 89 Days Past Due | Commercial mortgage | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	73	2,347
60 – 89 Days Past Due | Home equity loans and lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	10
60 – 89 Days Past Due | Home equity loans and lines | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
60 – 89 Days Past Due | Home equity loans and lines | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	10
60 – 89 Days Past Due | Residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	127	79
60 – 89 Days Past Due | Residential mortgage | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	64	0
60 – 89 Days Past Due | Residential mortgage | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	63	79
60 – 89 Days Past Due | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	1,083	0
60 – 89 Days Past Due | Construction | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	1,083	0
60 – 89 Days Past Due | Construction | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
60 – 89 Days Past Due | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	163	286
60 – 89 Days Past Due | Commercial and industrial | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	236
60 – 89 Days Past Due | Commercial and industrial | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	163	50
60 – 89 Days Past Due | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
60 – 89 Days Past Due | Consumer | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
60 – 89 Days Past Due | Consumer | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
60 – 89 Days Past Due | Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	829	177
60 – 89 Days Past Due | Leases | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	508	177
60 – 89 Days Past Due | Leases | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	321	0
Over 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Commercial mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Commercial mortgage | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Commercial mortgage | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Home equity loans and lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Home equity loans and lines | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Home equity loans and lines | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Residential mortgage | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Residential mortgage | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Construction | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Construction | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Commercial and industrial | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Commercial and industrial | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Consumer | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Consumer | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Leases | Originated
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Over 89 Days Past Due | Leases | Acquired
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, past due	0	0
Originated Loans | Administratively Delinquent
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, current	6,500	4,000
Acquired Loans | Administratively Delinquent
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, current	$ 297	$ 102