Acquisitions - Narrative (Details)		3 Months Ended		9 Months Ended
	Apr. 01, 2020 USD ($) shares	Sep. 30, 2020 USD ($) branch	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) branch	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Nov. 01, 2019 USD ($) branch $ / shares
Business Acquisition [Line Items]
Assets		$ 8,865,473,000		$ 8,865,473,000		$ 8,188,694,000
Net loans receivable		6,392,712,000		6,392,712,000		6,135,857,000
Liabilities		7,848,143,000		7,848,143,000		7,206,177,000
Deposits		6,629,648,000		6,629,648,000		5,645,842,000
Borrowings		1,015,210,000		1,015,210,000		$ 1,407,022,000
Merger-related expenses		424,000	$ 740,000	1,931,000	$ 1,202,000
Goodwill		$ 0		$ 0
Branch closures
Business Acquisition [Line Items]
Number of branches closed | branch		4		4
Loss on branch closures				$ 770,000
Stewardship Financial Corporation
Business Acquisition [Line Items]
Assets							$ 956,000,000.0
Net loans receivable							756,900,000
Securities							52,600,000
Liabilities							877,800,000
Deposits							781,400,000
Borrowings							$ 81,800,000
Number of stores | branch							12
Stewardship Financial Corporation
Business Acquisition [Line Items]
Business acquisition, share price (in dollars per share) | $ / shares							$ 15.75
Merger-related expenses		$ 248,000	740,000	1,300,000	1,200,000
Roselle Entities
Business Acquisition [Line Items]
Merger-related expenses		$ 175,000	$ 0	$ 618,000	$ 0
Business acquisition, equity interest issued or issuable (in shares) | shares	4,759,048
Goodwill	$ 23,809,000
Minimum | Equipment | Roselle Entities
Business Acquisition [Line Items]
Property, plant and equipment, useful life				3 years
Maximum | Equipment | Roselle Entities
Business Acquisition [Line Items]
Property, plant and equipment, useful life				10 years