Loans and the Allowance for Loan Losses (Details) - Aging analysis - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	$ 13,755	$ 5,734
Total Past Due and Nonaccrual	28,555	20,551
Current	3,863,872	3,458,890
Gross Loans	3,892,427	3,479,441
Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	951	1,460
Total Past Due and Nonaccrual	5,647	6,583
Current	635,966	546,993
Gross Loans	641,613	553,576
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	8,369	1,081
Total Past Due and Nonaccrual	17,012	8,256
Current	2,568,193	2,196,454
Gross Loans	2,585,205	2,204,710
Commercial Construction Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual
Total Past Due and Nonaccrual
Current	399,453	486,228
Gross Loans	399,453	486,228
Residential Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	4,435	3,193
Total Past Due and Nonaccrual	5,894	5,712
Current	258,350	226,835
Gross Loans	264,244	232,547
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual
Total Past Due and Nonaccrual	2
Current	1,910	2,380
Gross Loans	1,912	2,380
30 - 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual	1,703	7,534
30 - 59 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual	199	475
30 - 59 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual	586	4,928
30 - 59 Days Past Due [Member] | Commercial Construction Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual
30 - 59 Days Past Due [Member] | Residential Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual	918	2,131
30 - 59 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual
60 - 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual	8,888	1,990
60 - 89 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual	288	18
60 - 89 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual	8,057	1,584
60 - 89 Days Past Due [Member] | Commercial Construction Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual
60 - 89 Days Past Due [Member] | Residential Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual	541	388
60 - 89 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual	2
90 Days or Greater Past Due and Still Accruing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual	4,209	5,293
90 Days or Greater Past Due and Still Accruing [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual	4,209	4,630
90 Days or Greater Past Due and Still Accruing [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual		663
90 Days or Greater Past Due and Still Accruing [Member] | Commercial Construction Portfolio Segment [Member]
Financing Receivable, Recorded Investment, 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, Recorded Investment, 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, Recorded Investment, Past Due [Line Items]
Total Past Due and Nonaccrual