Allowance for Loan Losses - Age Analysis of Past Due Loans Segregated by Class of Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	$ 5,563,123	$ 5,002,925
Loans, Past Due	52,089	60,008
Non-performing loans	42,635	35,382
Total Loans	5,615,212	5,062,933
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	2,479,513	2,145,655
Loans, Past Due	18,963	20,948
Non-performing loans	16,172	8,719
Total Loans	2,498,476	2,166,603
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	1,391,475	1,244,802
Loans, Past Due	9,560	12,028
Non-performing loans	8,071	9,279
Total Loans	1,401,035	1,256,830
Commercial Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	450,410	401,084
Loans, Past Due	5,474	12,360
Non-performing loans	4,927	8,753
Total Loans	455,884	413,444
Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	689,635	631,085
Loans, Past Due	12,347	8,287
Non-performing loans	9,918	5,629
Total Loans	701,982	639,372
Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	476,866	465,055
Loans, Past Due	5,418	5,790
Non-performing loans	3,439	2,902
Total Loans	482,284	470,845
Installment and Other Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	65,525	73,486
Loans, Past Due	327	453
Non-performing loans	108	100
Total Loans	65,852	73,939
Consumer Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	5,906	6,579
Loans, Past Due	0	0
Non-performing loans	0	0
Total Loans	5,906	6,579
Loans Held for Sale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	3,793	35,179
Loans, Past Due	0	142
Non-performing loans	0	0
Total Loans	3,793	35,321
30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	6,598	22,001
30-59 Days Past Due | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	2,032	11,602
30-59 Days Past Due | Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	1,061	2,453
30-59 Days Past Due | Commercial Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	547	3,517
30-59 Days Past Due | Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	1,312	1,728
30-59 Days Past Due | Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	1,470	2,365
30-59 Days Past Due | Installment and Other Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	176	242
30-59 Days Past Due | Consumer Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	0	0
30-59 Days Past Due | Loans Held for Sale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	0	94
60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	2,856	2,625
60-89 Days Past Due | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	759	627
60-89 Days Past Due | Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	428	296
60-89 Days Past Due | Commercial Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	0	90
60-89 Days Past Due | Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	1,117	930
60-89 Days Past Due | Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	509	523
60-89 Days Past Due | Installment and Other Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	43	111
60-89 Days Past Due | Consumer Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	0	0
60-89 Days Past Due | Loans Held for Sale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	$ 0	$ 48