Loans and the Allowance for Loan Losses (Details) - Aging analysis - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Nonaccrual	$ 51,321	$ 51,855
Total Past Due and Nonaccrual	63,056	69,811
Current	5,052,417	4,475,088
Gross Loans	5,115,473	4,544,899
Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual	33,781	29,340
Total Past Due and Nonaccrual	44,129	32,660
Current	1,069,614	956,098
Gross Loans	1,113,743	988,758
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual	7,529	15,135
Total Past Due and Nonaccrual	8,218	23,137
Current	3,022,598	2,755,030
Gross Loans	3,030,816	2,778,167
Commercial Construction Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual	7,101	2,934
Total Past Due and Nonaccrual	7,101	5,994
Current	639,071	459,395
Gross Loans	646,172	465,389
Residential Real Estate Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual	2,910	4,446
Total Past Due and Nonaccrual	3,608	8,020
Current	318,699	301,971
Gross Loans	322,307	309,991
Consumer Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual
Total Past Due and Nonaccrual
Current	2,435	2,594
Gross Loans	2,435	2,594
30 - 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual	6,510	13,786
30 - 59 Days Past Due [Member] \| Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual	5,812	1,673
30 - 59 Days Past Due [Member] \| Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual		6,162
30 - 59 Days Past Due [Member] \| Commercial Construction Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual		2,496
30 - 59 Days Past Due [Member] \| Residential Real Estate Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual	698	3,455
30 - 59 Days Past Due [Member] \| Consumer Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual
60 - 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual	2,127	2,523
60 - 89 Days Past Due [Member] \| Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual	1,438
60 - 89 Days Past Due [Member] \| Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual	689	1,840
60 - 89 Days Past Due [Member] \| Commercial Construction Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual		564
60 - 89 Days Past Due [Member] \| Residential Real Estate Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual		119
60 - 89 Days Past Due [Member] \| Consumer Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual
90 Days or Greater Past Due and Still Accruing [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual	3,098	1,647
90 Days or Greater Past Due and Still Accruing [Member] \| Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual	3,098	1,647
90 Days or Greater Past Due and Still Accruing [Member] \| Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual
90 Days or Greater Past Due and Still Accruing [Member] \| Commercial Construction Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual
90 Days or Greater Past Due and Still Accruing [Member] \| Residential Real Estate Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual
90 Days or Greater Past Due and Still Accruing [Member] \| Consumer Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due and Nonaccrual