Loans Receivable, Net - Components of Loans Receivable, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans	$ 7,932,590	$ 6,214,652
Deferred origination costs, net	10,586	9,880
Loan receivable, allowance for credit losses	29,635	16,852	$ 16,705	$ 16,577
Total loans, net	7,913,541	6,207,680
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans	5,055,405	3,485,497
Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans	502,760	396,434
Commercial | Commercial real estate – owner occupied
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans	1,220,983	792,653
Commercial | Commercial real estate – investor
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans	3,331,662	2,296,410
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans	2,877,185	2,729,155
Loan receivable, allowance for credit losses	4,314	591	$ 367	$ 486
Consumer | Residential real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans	2,458,641	2,321,157
Consumer | Home equity loans and lines
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans	335,624	318,576
Consumer | Other consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans	$ 82,920	$ 89,422