Loans Receivable and Allowance for Loan Losses - Rollforward of Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Allowance for loan losses:
Beginning balance	$ 74,676	$ 61,709	$ 62,342
Provision (credited) charged	(9,953)	18,447	4,224
Recoveries	1,530	823	496
Charge-offs	(3,564)	(6,303)	(5,353)
Ending balance	62,689	74,676	61,709
Real estate loans | One-to-four family
Allowance for loan losses:
Beginning balance	13,586	13,780	15,232
Provision (credited) charged	(4,037)	1,299	(429)
Recoveries	22	438	30
Charge-offs	(773)	(1,931)	(1,053)
Ending balance	8,798	13,586	13,780
Real estate loans | Multifamily and commercial
Allowance for loan losses:
Beginning balance	30,681	22,980	23,251
Provision (credited) charged	(7,354)	7,713	(178)
Recoveries	1,231	16	10
Charge-offs	(703)	(28)	(103)
Ending balance	23,855	30,681	22,980
Real estate loans | Construction
Allowance for loan losses:
Beginning balance	11,271	7,435	7,217
Provision (credited) charged	(2,330)	3,835	216
Recoveries	2	1	2
Charge-offs	0	0	0
Ending balance	8,943	11,271	7,435
Commercial business loans
Allowance for loan losses:
Beginning balance	17,384	15,836	14,176
Provision (credited) charged	4,384	5,360	5,250
Recoveries	219	308	404
Charge-offs	(1,773)	(4,120)	(3,994)
Ending balance	20,214	17,384	15,836
Consumer loans | Home equity loans and advances
Allowance for loan losses:
Beginning balance	1,748	1,669	2,458
Provision (credited) charged	(623)	239	(638)
Recoveries	56	60	50
Charge-offs	(308)	(220)	(201)
Ending balance	873	1,748	1,669
Consumer loans | Other consumer loans
Allowance for loan losses:
Beginning balance	6	9	8
Provision (credited) charged	7	1	3
Recoveries	0	0	0
Charge-offs	(7)	(4)	(2)
Ending balance	$ 6	$ 6	$ 9