Loans - (Loan Portfolio Composition Including Carrying Value by Segment of Loans Accounted for under ASC Topic 310-30) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Loans [Line Items]
Total Loans	$ 3,702,334	$ 3,178,947	$ 2,953,655
% of Total	100.00%	100.00%
Commercial Loan [Member]
Loans [Line Items]
Total Loans	$ 2,105,899	$ 1,874,605
% of Total	56.90%	59.00%
Commercial Real Estate [Member]
Loans [Line Items]
Total Loans	$ 710,715	$ 563,049
% of Total	19.20%	17.70%
Residential Real Estate Segment [Member]
Loans [Line Items]
Total Loans	$ 859,155	$ 716,237
% of Total	23.20%	22.50%
Consumer [Member]
Loans [Line Items]
Total Loans	$ 26,565	$ 25,056
% of Total	0.70%	0.80%
ASC 310-30 [Member]
Loans [Line Items]
Total Loans	$ 112,309	$ 120,623	$ 140,064
ASC 310-30 [Member] | Commercial Loan [Member]
Loans [Line Items]
Total Loans	24,702	29,475
ASC 310-30 [Member] | Commercial Real Estate [Member]
Loans [Line Items]
Total Loans	75,277	77,908
ASC 310-30 [Member] | Residential Real Estate Segment [Member]
Loans [Line Items]
Total Loans	12,000	12,759
ASC 310-30 [Member] | Consumer [Member]
Loans [Line Items]
Total Loans	330	481
Originated and acquired loans [Member]
Loans [Line Items]
Total Loans	3,590,025	3,058,324
Originated and acquired loans [Member] | Commercial Loan [Member]
Loans [Line Items]
Total Loans	2,081,197	1,845,130
Originated and acquired loans [Member] | Commercial Real Estate [Member]
Loans [Line Items]
Total Loans	635,438	485,141
Originated and acquired loans [Member] | Residential Real Estate Segment [Member]
Loans [Line Items]
Total Loans	847,155	703,478
Originated and acquired loans [Member] | Consumer [Member]
Loans [Line Items]
Total Loans	$ 26,235	$ 24,575