Loans and the Allowance for Loan Losses (Details) - Credit quality indicators - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	$ 4,976,805	$ 4,544,899
Commercial Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	1,051,199	988,758
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	3,054,196	2,778,167
Commercial Construction Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	548,039	465,389
Residential Real Estate Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	319,215	309,991
Consumer Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	4,156	2,594
Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	4,874,375	4,456,187
Pass [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	997,975	951,610
Pass [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	3,024,553	2,742,989
Pass [Member] | Commercial Construction Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	533,103	453,598
Pass [Member] | Residential Real Estate Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	314,599	305,414
Pass [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	4,143	2,576
Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	37,342	21,460
Special Mention [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	17,452	3,371
Special Mention [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	12,970	12,574
Special Mention [Member] | Commercial Construction Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	6,920	5,515
Special Mention [Member] | Residential Real Estate Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans
Special Mention [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans
Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	65,088	67,252
Substandard [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	35,772	33,777
Substandard [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	16,673	22,604
Substandard [Member] | Commercial Construction Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	8,014	6,276
Substandard [Member] | Residential Real Estate Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	4,616	4,577
Substandard [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	13	18
Doubtful [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans
Doubtful [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans
Doubtful [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans
Doubtful [Member] | Commercial Construction Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans
Doubtful [Member] | Residential Real Estate Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans
Doubtful [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans