Loans Receivable and Allowance for Credit Losses - Narrative (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2022 USD ($) loan	Jun. 30, 2021 USD ($) loan	Jun. 30, 2022 USD ($) loan	Jun. 30, 2021 USD ($) loan	Dec. 31, 2021 USD ($) loan	Mar. 31, 2022 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable on loans receivable	$ 24,100,000		$ 24,100,000
Loans held-for-sale	0		0		$ 0
Proceeds from sales of loans held-for-sale			3,212,000	$ 274,980,000
Gain on sale of loans held-for-sale	0		110,000	8,400,000
Loss on sale of loans held-for-sale	0		0	0
Purchases of loans receivable	0		0	$ 71,590,000
Financing receivable, excluding accrued interest, before allowance for credit loss	6,982,796,000		6,982,796,000		6,360,601,000
Carrying value of servicing liability	$ 521,700,000		$ 521,700,000		$ 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	$ 4,500,000		$ 4,500,000		$ 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
Mortgage loans in process of foreclosure, amount	87,000		87,000		87,000
Specific allowance for loan losses attributable to impaired loans	385,000		385,000		378,000
Impaired loans for which there are no related allowance for loan losses	15,033,000		15,033,000		17,280,000
Financing receivable, modifications, recorded investment	$ 20,800,000		$ 20,800,000		22,400,000
Number of loans | loan	0	2	1	2
Off-balance sheet, credit loss, liability	$ 8,358,000		$ 8,358,000		524,000	$ 8,846,000
Off-balance sheet, credit loss, liability, credit loss expense (reversal)	(488,000)		160,000
Real estate loans | One-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sales of loans held-for-sale	589,000	$ 14,400,000	589,000	$ 15,600,000
Gain on sale of loans held-for-sale		277,000
Loss on sale of loans held-for-sale		$ 0
Specific allowance for loan losses attributable to impaired loans	246,000		246,000		258,000
Impaired loans for which there are no related allowance for loan losses	$ 1,146,000		$ 1,146,000		1,882,000
Number of loans | loan	0	1	0	1
Real estate loans | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sales of loans held-for-sale	$ 424,000	$ 31,000	$ 1,300,000	$ 6,400,000
Gain on sale of loans held-for-sale		0
Loss on sale of loans held-for-sale		0
Real estate loans | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sales of loans held-for-sale				4,100,000
Purchases of loans receivable		$ 71,600,000		$ 71,600,000
Specific allowance for loan losses attributable to impaired loans	97,000		97,000		97,000
Impaired loans for which there are no related allowance for loan losses	$ 13,406,000		$ 13,406,000		13,861,000
Number of loans | loan	0	1	0	1
Commercial business loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sales of loans held-for-sale		$ 244,700,000	$ 1,300,000	$ 248,900,000
Gain on sale of loans held-for-sale		7,700,000
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	168,000		168,000		573,000
Less Than 90 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual	$ 1,700,000		$ 1,700,000		$ 1,700,000
Financial receivable, number of loans in nonaccrual status | loan	10		10		10
60-89 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, modifications, recorded investment	$ 30,000		$ 30,000
Number of loans | loan			1
30-59 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, modifications, recorded investment					$ 36,000
Number of loans | loan			1		1
Freddie Mac
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from Sale of Loans Receivable	0		$ 0
Gain on sale of loans receivable		544,000		2,300,000
Loss on sale of loans receivable		0		0
Proceeds from securitizations of loans held-for-investment		$ 35,600,000		$ 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	2,100,000		2,100,000		$ 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	185,000		185,000		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	3,800,000		3,800,000		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	15,300,000		15,300,000
Paycheck Protection Program | Commercial business loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, excluding accrued interest, before allowance for credit loss	10,600,000		10,600,000		44,900,000
Financing receivable, unamortized loan fee	$ 269,000		$ 269,000		$ 1,200,000