Loans and Allowance for Credit Losses on Loans - Narrative (Details)				3 Months Ended		9 Months Ended
	Sep. 22, 2022 USD ($) security	May 05, 2022 USD ($) security	May 07, 2021 USD ($) security	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Loans and Leases Receivable Disclosure [Line Items]
Proceeds from sale of loans receivable							$ 262,086,000
Net gain (loss) on sale of loans				$ 13,354,000	$ 29,013,000	$ 52,883,000	82,755,000
Purchases of available for sale securities						50,274,000	195,206,000
Servicing rights				144,984,000		144,984,000		$ 110,348,000
Purchase of loans						289,030,000	$ 312,992,000
Payments to held to maturity security						1,005,487,000
Provision for credit losses				1,709,000		8,458,000
Loan Sale and Freddie Mac Q Series Securitization
Loans and Leases Receivable Disclosure [Line Items]
Net gain (loss) on sale of loans		$ 2,300,000	$ (676,000)
First loss position in loan portfolio, maximum securitization pool, percentage		12.00%	10.00%
First loss position in loan portfolio, maximum securitization pool, amount		$ 25,700,000	$ 26,200,000
First loss position in loan portfolio, reserves for losses		1,200,000	1,400,000
Servicing rights		1,200,000	$ 730,000
Amortization of security				0		0
Gain (loss) on sale				0		0
Loan Sale and Freddie Mac Q Series Securitization | Other liabilities
Loans and Leases Receivable Disclosure [Line Items]
Non-contingent reserve		$ 2,500,000
Loan Sale and Freddie Mac Q Series Securitization | Mortgage-backed Securities, Purchased from Freddie Mac
Loans and Leases Receivable Disclosure [Line Items]
Number of securities purchased | security		0	2
Purchases of available for sale securities			$ 28,700,000
Loan Sale and Freddie Mac Q Series Securitization | US Treasury Securities.
Loans and Leases Receivable Disclosure [Line Items]
Purchases of available for sale securities		$ 27,000,000.0
Multi-family financing
Loans and Leases Receivable Disclosure [Line Items]
Provision for credit losses				$ (2,365,000)		$ (605,000)
Multi-family financing | Loan Sale and Freddie Mac Q Series Securitization
Loans and Leases Receivable Disclosure [Line Items]
Amount of portfolio of loans sold in a securitization transaction		$ 214,000,000.0	$ 262,000,000.0
Multi-family financing | Loan Sale and Securitization
Loans and Leases Receivable Disclosure [Line Items]
Amount of portfolio of loans sold in a securitization transaction	$ 1,200,000,000
Number of securities purchased | security	1
Net gain (loss) on sale of loans	$ (525,000)
Payments to held to maturity security	$ 1,000,000.0
Percentage of first loss position	13.40%
Proceeds and accrued interest on loans, net of the acquired securities	$ 150,600,000
Allowance for credit losses associated with loans sold released through the provision for credit losses	4,000,000.0
Pricing loss	5,400,000
Transaction expenses	4,900,000
Capitalizing servicing rights	6,700,000
Release of deferred fees on loans sold	$ 3,200,000