Loans and Allowance for Credit Losses (Details 5) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Loans past due	$ 55,200	$ 46,310
Current loans	6,547,326	6,365,218
Total recorded investment in loans	6,602,526	6,411,528
Real Estate Mortgage - Residential [Member]
Loans past due	8,335	9,012
Current loans	95,597	95,345
Total recorded investment in loans	103,932	104,357
Owner Occupied - Commercial Real Estate - [Member]
Loans past due	9,802	9,929
Current loans	790,945	745,515
Total recorded investment in loans	800,747	755,444
Other Consumer [Member]
Loans past due	113	142
Current loans	3,110	3,456
Total recorded investment in loans	3,223	3,598
Income Producing - Commercial Real Estate [Member]
Loans past due	18,064	12,160
Current loans	3,119,434	3,034,934
Total recorded investment in loans	3,137,498	3,047,094
Home Equity [Member]
Loans past due	584	801
Current loans	89,687	92,463
Total recorded investment in loans	90,271	93,264
Construction - Commercial And Residencial [Member]
Loans past due	7,319	7,320
Current loans	1,033,494	1,024,512
Total recorded investment in loans	1,040,813	1,031,832
Commercial [Member]
Loans past due	10,983	6,946
Current loans	1,415,059	1,368,993
Total recorded investment in loans	1,426,042	1,375,939
Financing Receivables, 30 to 59 Days Past Due [Member]
Loans past due	29,562	14,970
Financing Receivables, 30 to 59 Days Past Due [Member] | Real Estate Mortgage - Residential [Member]
Loans past due	1,745	6,993
Financing Receivables, 30 to 59 Days Past Due [Member] | Owner Occupied - Commercial Real Estate - [Member]
Loans past due	5,361	522
Financing Receivables, 30 to 59 Days Past Due [Member] | Other Consumer [Member]
Loans past due	91	45
Financing Receivables, 30 to 59 Days Past Due [Member] | Income Producing - Commercial Real Estate [Member]
Loans past due	13,452	4,398
Financing Receivables, 30 to 59 Days Past Due [Member] | Home Equity [Member]
Loans past due		307
Financing Receivables, 30 to 59 Days Past Due [Member] | Construction - Commercial And Residencial [Member]
Loans past due
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial [Member]
Loans past due	6,179	2,705
Financing Receivables, 60 to 89 Days Past Due [Member]
Loans past due	12,251	18,102
Financing Receivables, 60 to 89 Days Past Due [Member] | Real Estate Mortgage - Residential [Member]
Loans past due		1,244
Financing Receivables, 60 to 89 Days Past Due [Member] | Owner Occupied - Commercial Real Estate - [Member]
Loans past due	1,105	3,906
Financing Receivables, 60 to 89 Days Past Due [Member] | Other Consumer [Member]
Loans past due	17	6
Financing Receivables, 60 to 89 Days Past Due [Member] | Income Producing - Commercial Real Estate [Member]
Loans past due	4,562	6,930
Financing Receivables, 60 to 89 Days Past Due [Member] | Home Equity [Member]
Loans past due	90
Financing Receivables, 60 to 89 Days Past Due [Member] | Construction - Commercial And Residencial [Member]
Loans past due	5,268	5,268
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial [Member]
Loans past due	1,209	748
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans past due	13,387	13,238
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Real Estate Mortgage - Residential [Member]
Loans past due	6,590	775
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Owner Occupied - Commercial Real Estate - [Member]
Loans past due	3,336	5,501
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Other Consumer [Member]
Loans past due	5	91
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Income Producing - Commercial Real Estate [Member]
Loans past due	50	832
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Home Equity [Member]
Loans past due	494	494
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Construction - Commercial And Residencial [Member]
Loans past due	2,051	2,052
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial [Member]
Loans past due	$ 3,595	$ 3,493