Loans Receivable and Allowance for Credit Losses - Narrative (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022 USD ($) loan	Sep. 30, 2021 USD ($) loan	Sep. 30, 2022 USD ($) loan	Sep. 30, 2021 USD ($) loan	Dec. 31, 2021 USD ($) loan	Jun. 30, 2022 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable on loans receivable	$ 26,300,000		$ 26,300,000
Loans held-for-sale	0		0		$ 0
Proceeds from sales of loans held-for-sale			6,187,000	$ 293,005,000
Gain on sale of loans held-for-sale	63,000		173,000	8,600,000
Loss on sale of loans held-for-sale	64,000		64,000	0
Purchases of loans receivable	0		0	$ 74,232,000
Financing receivable, excluding accrued interest, before allowance for credit loss	7,326,223,000		7,326,223,000		6,360,601,000
Carrying value of servicing liability	$ 507,600,000		$ 507,600,000		$ 519,500,000
Threshold period, past due status of financial receivables			30 days
Threshold period, past due for nonperforming status of financial receivables	90 days		90 days		90 days
Non-accrual	$ 7,000,000		$ 7,000,000		$ 3,900,000
Financing receivable, excluding accrued interest, 90 days or more past due, still accruing	0		0		0
Real estate owned	$ 0		$ 0		0
Number of loans | loan	0	1	1	3
Mortgage loans in process of foreclosure, amount					87,000
Specific allowance for loan losses attributable to impaired loans	$ 330,000		$ 330,000		378,000
Impaired loans for which there are no related allowance for loan losses	16,697,000		16,697,000		17,280,000
Financing receivable, modifications, recorded investment	20,100,000		20,100,000		22,400,000
Off-balance sheet, credit loss, liability	6,611,000		6,611,000		524,000	$ 8,358,000
Off-balance sheet, credit loss, liability, credit loss expense (reversal)	(1,747,000)		(1,587,000)
Real estate loans | One-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sales of loans held-for-sale	$ 1,800,000	$ 1,800,000	$ 2,400,000	$ 17,400,000
Purchases of loans receivable		$ 678,000		$ 678,000
Number of loans | loan	0	1	0	2
Specific allowance for loan losses attributable to impaired loans	$ 213,000		$ 213,000		258,000
Impaired loans for which there are no related allowance for loan losses	1,319,000		1,319,000		1,882,000
Real estate loans | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sales of loans held-for-sale	510,000		$ 1,800,000	$ 6,400,000
Real estate loans | Multifamily And Commercial Real Estate Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sales of loans held-for-sale				19,100,000
Real estate loans | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchases of loans receivable		$ 2,000,000		$ 73,600,000
Number of loans | loan			0	1
Specific allowance for loan losses attributable to impaired loans	98,000		$ 98,000		97,000
Impaired loans for which there are no related allowance for loan losses	14,924,000		14,924,000		13,861,000
Commercial business loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sales of loans held-for-sale	685,000	1,200,000	2,000,000	$ 250,100,000
Gain on sale of loans held-for-sale		140,000
Loss on sale of loans held-for-sale		0
Specific allowance for loan losses attributable to impaired loans	10,000		10,000		16,000
Impaired loans for which there are no related allowance for loan losses	156,000		156,000		573,000
Commercial business loans | Multifamily And Commercial Real Estate Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sales of loans held-for-sale		15,000,000
Less Than 90 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual	$ 1,800,000		$ 1,800,000		$ 1,700,000
Financial receivable, number of loans in nonaccrual status | loan	11		11		10
60-89 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan			2
Financing receivable, modifications, recorded investment	$ 353,000		$ 353,000
30-59 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan			0		1
Financing receivable, modifications, recorded investment					$ 36,000
Freddie Mac
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from Sale of Loans Receivable	0	$ 0	$ 0
Gain on sale of loans receivable				2,300,000
Loss on sale of loans receivable				0
Proceeds from securitizations of loans held-for-investment				$ 99,600,000
Stewardship Financial Corporation | Financial Asset Acquired with Credit Deterioration
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, excluding accrued interest, before allowance for credit loss	2,000,000		2,000,000		2,700,000
Roselle Entities | Financial Asset Acquired with Credit Deterioration
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, excluding accrued interest, before allowance for credit loss	184,000		184,000		184,000
Freehold Entities | Financial Asset Acquired with Credit Deterioration
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, excluding accrued interest, before allowance for credit loss	3,700,000		3,700,000		3,900,000
RSI Entites | Financial Asset Acquired with Credit Deterioration
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, excluding accrued interest, before allowance for credit loss	13,900,000		13,900,000
Paycheck Protection Program | Commercial business loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, excluding accrued interest, before allowance for credit loss	2,200,000		2,200,000		44,900,000
Financing receivable, unamortized loan fee	$ 44,000		$ 44,000		$ 1,200,000