Loans Receivable, Net - Components of Loans Receivable, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans receivable	$ 8,181,832		$ 7,756,106
Deferred origination costs, net	8,282		9,486
Allowance for loan credit losses	(50,153)	$ (53,876)	(60,735)	$ (56,350)	$ (38,509)	$ (16,852)
Total loans receivable, net	8,139,961		7,704,857
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans receivable	5,504,630		5,107,185
Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans receivable	457,674		470,656
Commercial | Commercial and industrial | Paycheck Protection Program
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans receivable	52,500		95,400
Commercial | Commercial real estate – owner occupied
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans receivable	1,123,973		1,145,065
Commercial | Commercial real estate – investor
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans receivable	3,922,983		3,491,464
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans receivable	2,677,202		2,648,921
Allowance for loan credit losses	(1,641)	$ (1,267)	(1,770)	$ (3,248)	$ (4,220)	$ (591)
Consumer | Residential real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans receivable	2,401,240		2,309,459
Consumer | Home equity loans and lines and other consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Total loans receivable	$ 275,962		$ 339,462