Loans and the Allowance for Loan Losses (Details) - Allowance for loan and lease losses - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
ALLL
ALLL, Individually evaluated for impairment	$ 1,386		$ 36
ALLL, Collectively evaluated for impairment	36,185		33,718
ALLL, Acquired portfolio	1,200		1,200
ALLL, Acquired with deteriorated credit quality
Total	38,771	$ 37,698	34,954	$ 34,749	$ 33,594	$ 31,748
Gross loans
Loans Receivable, Individually evaluated for impairment	67,896		59,932
Loans Receivable, Collectively evaluated for impairment	4,499,769		4,171,343
Loans Receivable, Acquired portfolio	541,226		311,115
Loans Receivables, Acquired with deteriorated credit quality	6,582		2,509
Total	5,115,473		4,544,899
Commercial Portfolio Segment [Member]
ALLL
ALLL, Individually evaluated for impairment
ALLL, Collectively evaluated for impairment	8,125		9,675
ALLL, Acquired portfolio	200		200
ALLL, Acquired with deteriorated credit quality
Total	8,325	8,721	9,875	9,949	8,960	8,233
Gross loans
Loans Receivable, Individually evaluated for impairment	41,030		29,896
Loans Receivable, Collectively evaluated for impairment	977,895		949,129
Loans Receivable, Acquired portfolio	89,359		7,224
Loans Receivables, Acquired with deteriorated credit quality	5,459		2,509
Total	1,113,743		988,758
Commercial Real Estate Portfolio Segment [Member]
ALLL
ALLL, Individually evaluated for impairment	23		7
ALLL, Collectively evaluated for impairment	19,987		17,840
ALLL, Acquired portfolio	1,000		1,000
ALLL, Acquired with deteriorated credit quality
Total	21,010	21,485	18,847	18,228	18,221	17,112
Gross loans
Loans Receivable, Individually evaluated for impairment	12,524		18,327
Loans Receivable, Collectively evaluated for impairment	2,645,903		2,500,132
Loans Receivable, Acquired portfolio	371,266		259,708
Loans Receivables, Acquired with deteriorated credit quality	1,123
Total	3,030,816		2,778,167
Commercial Construction Portfolio Segment [Member]
ALLL
ALLL, Individually evaluated for impairment	1,339
ALLL, Collectively evaluated for impairment	5,836		4,519
ALLL, Acquired portfolio
ALLL, Acquired with deteriorated credit quality
Total	7,175	5,542	4,519	4,790	4,812	4,747
Gross loans
Loans Receivable, Individually evaluated for impairment	12,545		9,240
Loans Receivable, Collectively evaluated for impairment	597,352		456,149
Loans Receivable, Acquired portfolio	36,275
Loans Receivables, Acquired with deteriorated credit quality
Total	646,172		465,389
Residential Real Estate Portfolio Segment [Member]
ALLL
ALLL, Individually evaluated for impairment	24		29
ALLL, Collectively evaluated for impairment	1,737		1,237
ALLL, Acquired portfolio
ALLL, Acquired with deteriorated credit quality
Total	1,761	1,208	1,266	1,215	1,167	1,050
Gross loans
Loans Receivable, Individually evaluated for impairment	1,797		2,469
Loans Receivable, Collectively evaluated for impairment	276,457		263,449
Loans Receivable, Acquired portfolio	44,053		44,073
Loans Receivables, Acquired with deteriorated credit quality
Total	322,307		309,991
Consumer Portfolio Segment [Member]
ALLL
ALLL, Individually evaluated for impairment
ALLL, Collectively evaluated for impairment	4		2
ALLL, Acquired portfolio
ALLL, Acquired with deteriorated credit quality
Total	4	2	2	3	3	1
Gross loans
Loans Receivable, Individually evaluated for impairment
Loans Receivable, Collectively evaluated for impairment	2,162		2,484
Loans Receivable, Acquired portfolio	273		110
Loans Receivables, Acquired with deteriorated credit quality
Total	2,435		2,594
Unallocated [Member]
ALLL
ALLL, Individually evaluated for impairment
ALLL, Collectively evaluated for impairment	496		445
ALLL, Acquired portfolio
ALLL, Acquired with deteriorated credit quality
Total	$ 496	$ 740	$ 445	$ 564	$ 431	$ 605