Loans Receivable and Allowance for Credit Losses - Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2022		Jun. 30, 2021	Jun. 30, 2022		Jun. 30, 2021
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 47,162		$ 71,904	$ 62,689	[1]	$ 74,676
Initial allowance related to PCD loans	633			633
Provision for (reversal of) credit losses	2,683		(1,761)	3,488		(3,041)
Recoveries	233		1,087	401		1,124
Charge-offs	(128)		(1,332)	(185)		(2,861)
Balance at end of period	50,583	[1]	69,898	50,583	[1]	69,898
Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(16,443)
Real estate loans | One-to-four family
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	8,814		19,850	8,798		13,586
Initial allowance related to PCD loans	131			131
Provision for (reversal of) credit losses	1,785		(2,463)	3,970		4,014
Recoveries	199		11	338		14
Charge-offs	(93)		(290)	(93)		(506)
Balance at end of period	10,836		17,108	10,836		17,108
Real estate loans | One-to-four family | Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(2,308)
Real estate loans | Multifamily
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	11,203		6,955	7,741		8,897
Initial allowance related to PCD loans	0			0
Provision for (reversal of) credit losses	(271)		1,783	5,221		(159)
Recoveries	0		0	0		0
Charge-offs	0		(296)	0		(296)
Balance at end of period	10,932		8,442	10,932		8,442
Real estate loans | Multifamily | Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(2,030)
Real estate loans | Commercial real estate
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	13,513		16,894	16,114		21,784
Initial allowance related to PCD loans	474			474
Provision for (reversal of) credit losses	493		89	2,119		(4,641)
Recoveries	0		931	0		937
Charge-offs	0		(100)	0		(266)
Balance at end of period	14,480		17,814	14,480		17,814
Real estate loans | Commercial real estate | Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(4,227)
Real estate loans | Construction
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	4,974		11,464	8,943		11,271
Initial allowance related to PCD loans	3			3
Provision for (reversal of) credit losses	593		(2,304)	(1,030)		(2,112)
Recoveries	0		0	0		1
Charge-offs	0		0	0		0
Balance at end of period	5,570		9,160	5,570		9,160
Real estate loans | Construction | Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(2,346)
Commercial business loans
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	7,143		14,804	20,214		17,384
Initial allowance related to PCD loans	19			19
Provision for (reversal of) credit losses	127		1,600	(7,640)		91
Recoveries	30		111	55		127
Charge-offs	(35)		(617)	(62)		(1,704)
Balance at end of period	7,284		15,898	7,284		15,898
Commercial business loans | Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(5,302)
Consumer loans | Home equity loans and advances
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	1,507		1,931	873		1,748
Initial allowance related to PCD loans	6			6
Provision for (reversal of) credit losses	(46)		(465)	840		(235)
Recoveries	4		34	8		45
Charge-offs	0		(29)	(27)		(87)
Balance at end of period	1,471		1,471	1,471		1,471
Consumer loans | Home equity loans and advances | Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				(229)
Consumer loans | Other consumer loans
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	8		6	6		6
Initial allowance related to PCD loans	0			0
Provision for (reversal of) credit losses	2		(1)	8		1
Recoveries	0		0	0		0
Charge-offs	0		0	(3)		(2)
Balance at end of period	$ 10		$ 5	10		$ 5
Consumer loans | Other consumer loans | Effect of adopting ASU No. 2016-13 ("CECL")
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				$ (1)

[1]  (1) The Company adopted ASU 2016-13 as of January 1, 2022. Prior year periods have not been restated.