Loans Receivable and Allowance for Credit Losses - Rollforward of Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Allowance for loan losses:
Balance at beginning of period	$ 62,689	$ 74,676	$ 61,709
Initial allowance related to PCD loans	633	0	0
Provision for (reversal of) credit losses	5,969	(9,953)	18,447
Recoveries	593	1,530	823
Charge-offs	(638)	(3,564)	(6,303)
Balance at end of period	52,803	62,689	74,676
Impact of adopting ASU 2016-13 (CECL) effective January 1, 2022
Allowance for loan losses:
Balance at beginning of period	(16,443)	0	0
Balance at end of period		(16,443)	0
Real estate loans \| One-to-four family
Allowance for loan losses:
Balance at beginning of period	8,798	13,586	13,780
Initial allowance related to PCD loans	131
Provision for (reversal of) credit losses	5,225	(4,037)	1,299
Recoveries	338	22	438
Charge-offs	(382)	(773)	(1,931)
Balance at end of period	11,802	8,798	13,586
Real estate loans \| One-to-four family \| Impact of adopting ASU 2016-13 (CECL) effective January 1, 2022
Allowance for loan losses:
Balance at beginning of period	(2,308)
Balance at end of period		(2,308)
Real estate loans \| Multifamily
Allowance for loan losses:
Balance at beginning of period	7,741	8,799	6,434
Initial allowance related to PCD loans	0
Provision for (reversal of) credit losses	2,166	(978)	2,365
Recoveries	0	216	0
Charge-offs	0	(296)	0
Balance at end of period	7,877	7,741	8,799
Real estate loans \| Multifamily \| Impact of adopting ASU 2016-13 (CECL) effective January 1, 2022
Allowance for loan losses:
Balance at beginning of period	(2,030)
Balance at end of period		(2,030)
Real estate loans \| Commercial real estate
Allowance for loan losses:
Balance at beginning of period	16,114	21,882	16,546
Initial allowance related to PCD loans	474
Provision for (reversal of) credit losses	5,750	(6,376)	5,348
Recoveries	0	1,015	16
Charge-offs	0	(407)	(28)
Balance at end of period	18,111	16,114	21,882
Real estate loans \| Commercial real estate \| Impact of adopting ASU 2016-13 (CECL) effective January 1, 2022
Allowance for loan losses:
Balance at beginning of period	(4,227)
Balance at end of period		(4,227)
Real estate loans \| Construction
Allowance for loan losses:
Balance at beginning of period	8,943	11,271	7,435
Initial allowance related to PCD loans	3
Provision for (reversal of) credit losses	(175)	(2,330)	3,835
Recoveries	0	2	1
Charge-offs	0	0	0
Balance at end of period	6,425	8,943	11,271
Real estate loans \| Construction \| Impact of adopting ASU 2016-13 (CECL) effective January 1, 2022
Allowance for loan losses:
Balance at beginning of period	(2,346)
Balance at end of period		(2,346)
Commercial business loans
Allowance for loan losses:
Balance at beginning of period	20,214	17,384	15,836
Initial allowance related to PCD loans	19
Provision for (reversal of) credit losses	(8,052)	4,384	5,360
Recoveries	208	219	308
Charge-offs	(190)	(1,773)	(4,120)
Balance at end of period	6,897	20,214	17,384
Commercial business loans \| Impact of adopting ASU 2016-13 (CECL) effective January 1, 2022
Allowance for loan losses:
Balance at beginning of period	(5,302)
Balance at end of period		(5,302)
Consumer loans \| Home equity loans and advances
Allowance for loan losses:
Balance at beginning of period	873	1,748	1,669
Initial allowance related to PCD loans	6
Provision for (reversal of) credit losses	1,019	(623)	239
Recoveries	45	56	60
Charge-offs	(33)	(308)	(220)
Balance at end of period	1,681	873	1,748
Consumer loans \| Home equity loans and advances \| Impact of adopting ASU 2016-13 (CECL) effective January 1, 2022
Allowance for loan losses:
Balance at beginning of period	(229)
Balance at end of period		(229)
Consumer loans \| Other consumer loans
Allowance for loan losses:
Balance at beginning of period	6	6	9
Initial allowance related to PCD loans	0
Provision for (reversal of) credit losses	36	7	1
Recoveries	2	0	0
Charge-offs	(33)	(7)	(4)
Balance at end of period	10	6	$ 6
Consumer loans \| Other consumer loans \| Impact of adopting ASU 2016-13 (CECL) effective January 1, 2022
Allowance for loan losses:
Balance at beginning of period	$ (1)
Balance at end of period		$ (1)

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- Definition

Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446

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- Definition

Amount, excluding accrued interest, of increase in allowance for credit loss on financing receivable from recovery. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (e)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

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- Definition

Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

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- Definition

Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

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- Definition

Amount, excluding accrued interest, of allowance for credit loss at acquisition date of financing receivable purchased with credit deterioration. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 19
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919265-210447

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