Loans and the Allowance for Loan Losses (Details) - Composition of loan portfolio - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 5,115,473	$ 4,544,899
Net deferred loan fees	(5,002)	(3,807)
Total loans receivable	5,110,471	4,541,092
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	1,113,743	988,758
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	3,030,816	2,778,167
Commercial Construction Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	646,172	465,389
Residential Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	322,307	309,991
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 2,435	$ 2,594