Loans Receivable and Allowance for Loan Losses - Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Allowance for loan losses:
Beginning balance	$ 62,524	$ 52,066	$ 58,178	$ 51,849
Provision for loan losses	1,500	5,676	5,900	6,426
Recoveries	149	279	518	556
Charge-offs	(767)	(3,388)	(1,190)	(4,198)
Ending balance	63,406	54,633	63,406	54,633
Real estate loans \| One-to-four family
Allowance for loan losses:
Beginning balance	18,549	18,762	19,991	18,599
Provision for loan losses	(809)	631	(2,362)	1,058
Recoveries	108	150	280	265
Charge-offs	(323)	(1,010)	(384)	(1,389)
Ending balance	17,525	18,533	17,525	18,533
Real estate loans \| Multifamily and commercial
Allowance for loan losses:
Beginning balance	22,802	18,085	19,933	17,616
Provision for loan losses	965	743	3,962	1,417
Recoveries	0	75	0	75
Charge-offs	0	(874)	(128)	(1,079)
Ending balance	23,767	18,029	23,767	18,029
Real estate loans \| Construction
Allowance for loan losses:
Beginning balance	6,728	4,598	5,217	4,598
Provision for loan losses	420	701	1,928	701
Recoveries	0	0	3	0
Charge-offs	0	0	0	0
Ending balance	7,148	5,299	7,148	5,299
Commercial business loans
Allowance for loan losses:
Beginning balance	10,920	6,563	8,275	6,358
Provision for loan losses	1,118	2,338	3,902	2,541
Recoveries	24	14	111	163
Charge-offs	(197)	(435)	(423)	(582)
Ending balance	11,865	8,480	11,865	8,480
Consumer loans \| Home equity loans and advances
Allowance for loan losses:
Beginning balance	2,870	3,965	4,577	4,231
Provision for loan losses	202	1,251	(1,607)	1,042
Recoveries	17	40	119	53
Charge-offs	(246)	(1,066)	(246)	(1,136)
Ending balance	2,843	4,190	2,843	4,190
Consumer loans \| Other consumer loans
Allowance for loan losses:
Beginning balance	7	8	8	11
Provision for loan losses	1	3	3	9
Recoveries	0	0	5	0
Charge-offs	(1)	(3)	(9)	(12)
Ending balance	7	8	7	8
Unallocated
Allowance for loan losses:
Beginning balance	648	85	177	436
Provision for loan losses	(397)	9	74	(342)
Recoveries	0	0	0	0
Charge-offs	0	0	0	0
Ending balance	$ 251	$ 94	$ 251	$ 94

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

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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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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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.

+ References

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

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