Loans Receivable and Allowance for Loan Losses - Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Allowance for loan losses:
Beginning balance	$ 62,771	$ 59,952	$ 62,342	$ 58,178
Provision for loan losses	112	2,400	548	4,400
Recoveries	58	189	399	369
Charge-offs	(538)	(17)	(886)	(423)
Ending balance	62,403	62,524	62,403	62,524
Real estate loans \| One-to-four family
Allowance for loan losses:
Beginning balance	17,375	18,828	15,232	19,991
Provision for loan losses	(1,254)	(324)	868	(1,552)
Recoveries	4	51	25	171
Charge-offs	(515)	(6)	(515)	(61)
Ending balance	15,610	18,549	15,610	18,549
Real estate loans \| Multifamily and commercial
Allowance for loan losses:
Beginning balance	20,986	19,097	23,251	19,933
Provision for loan losses	1,693	3,705	(572)	2,998
Recoveries	0	0	0	0
Charge-offs	0	0	0	(129)
Ending balance	22,679	22,802	22,679	22,802
Real estate loans \| Construction
Allowance for loan losses:
Beginning balance	9,033	6,574	7,217	5,217
Provision for loan losses	(228)	154	1,588	1,508
Recoveries	1	0	1	3
Charge-offs	0	0	0	0
Ending balance	8,806	6,728	8,806	6,728
Commercial business loans
Allowance for loan losses:
Beginning balance	12,225	10,800	14,176	8,275
Provision for loan losses	441	87	(1,555)	2,783
Recoveries	53	36	366	87
Charge-offs	(1)	(3)	(269)	(225)
Ending balance	12,718	10,920	12,718	10,920
Consumer loans \| Home equity loans and advances
Allowance for loan losses:
Beginning balance	3,146	3,924	2,458	4,577
Provision for loan losses	(542)	(1,153)	219	(1,810)
Recoveries	0	99	7	103
Charge-offs	(21)	0	(101)	0
Ending balance	2,583	2,870	2,583	2,870
Consumer loans \| Other consumer loans
Allowance for loan losses:
Beginning balance	6	7	8	8
Provision for loan losses	2	5	0	2
Recoveries	0	3	0	5
Charge-offs	(1)	(8)	(1)	(8)
Ending balance	7	7	7	7
Unallocated
Allowance for loan losses:
Beginning balance	0	722	0	177
Provision for loan losses	0	(74)	0	471
Recoveries	0	0	0	0
Charge-offs	0	0	0	0
Ending balance	$ 0	$ 648	$ 0	$ 648

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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