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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Allowance for loan losses:
Beginning balance	$ 59,952	$ 51,908	$ 58,178	$ 51,849
Provision for loan losses	2,400	375	4,400	751
Recoveries	189	172	369	277
Charge-offs	(17)	(389)	(423)	(811)
Ending balance	62,524	52,066	62,524	52,066
Real estate loans \| One-to-four family
Allowance for loan losses:
Beginning balance	18,828	18,818	19,991	18,599
Provision for loan losses	(324)	48	(1,552)	428
Recoveries	51	93	171	115
Charge-offs	(6)	(197)	(61)	(380)
Ending balance	18,549	18,762	18,549	18,762
Real estate loans \| Multifamily and commercial
Allowance for loan losses:
Beginning balance	19,097	17,638	19,933	17,616
Provision for loan losses	3,705	485	2,998	674
Recoveries	0	0	0	0
Charge-offs	0	(38)	(129)	(205)
Ending balance	22,802	18,085	22,802	18,085
Real estate loans \| Construction
Allowance for loan losses:
Beginning balance	6,574	4,253	5,217	4,598
Provision for loan losses	154	345	1,508	0
Recoveries	0	0	3	0
Charge-offs	0	0	0	0
Ending balance	6,728	4,598	6,728	4,598
Commercial business loans
Allowance for loan losses:
Beginning balance	10,800	7,014	8,275	6,358
Provision for loan losses	87	(376)	2,783	204
Recoveries	36	73	87	149
Charge-offs	(3)	(148)	(225)	(148)
Ending balance	10,920	6,563	10,920	6,563
Consumer loans \| Home equity loans and advances
Allowance for loan losses:
Beginning balance	3,924	4,129	4,577	4,231
Provision for loan losses	(1,153)	(170)	(1,810)	(209)
Recoveries	99	6	103	13
Charge-offs	0	0	0	(70)
Ending balance	2,870	3,965	2,870	3,965
Consumer loans \| Other consumer loans
Allowance for loan losses:
Beginning balance	7	10	8	11
Provision for loan losses	5	4	2	5
Recoveries	3	0	5	0
Charge-offs	(8)	(6)	(8)	(8)
Ending balance	7	8	7	8
Unallocated
Allowance for loan losses:
Beginning balance	722	46	177	436
Provision for loan losses	(74)	39	471	(351)
Recoveries	0	0	0	0
Charge-offs	0	0	0	0
Ending balance	$ 648	$ 85	$ 648	$ 85

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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