Loans receivable (Details 2) - USD ($) $ in Thousands	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment, Individually evaluated			$ 3,400
Loans individually evaluated for impairment, Acquired with deteriorated credit quality			2,310
Loans individually evaluated for impairment, Total allowance			0
Loans collectively evaluated for impairment, Ending loans balance	$ 1,473		1,515
Allowance for loan losses	1,473	$ 1,476	1,515	$ 1,568	$ 1,568	$ 1,568
Ending allowance attributed to loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment, Ending loans balance			0
Loans collectively evaluated for impairment, Ending loans balance	1,273		1,315
Allowance for loan losses	1,273		1,315
Ending loans balance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment, Ending loans balance			5,710
Loans collectively evaluated for impairment, Ending loans balance	243,790		239,278
Allowance for loan losses	249,549		244,988
Unallocated Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment, Total allowance			0
Loans collectively evaluated for impairment, Ending loans balance	200		200
Allowance for loan losses	200		200
Residential Real Estate One To Four Family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment, Individually evaluated	3,941		3,400
Loans individually evaluated for impairment, Acquired with deteriorated credit quality	1,818		2,146
Loans individually evaluated for impairment, Ending loans balance	0			0
Loans individually evaluated for impairment, Total allowance	0		0
Loans collectively evaluated for impairment, Total allowance	801		862
Allowance for loan losses	801	803	862	1,045	1,060	1,059
Residential Real Estate One To Four Family [Member] | Ending allowance attributed to loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment, Ending loans balance	0		0
Loans collectively evaluated for impairment, Ending loans balance	801		862
Residential Real Estate One To Four Family [Member] | Ending loans balance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment, Ending loans balance	5,759		5,546
Loans collectively evaluated for impairment, Ending loans balance	185,906		180,579
Residential Real Estate One To Four Family [Member] | Unallocated Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment, Total allowance	0		0
Loans collectively evaluated for impairment, Total allowance	0		0
Residential Real Estate Multi Family [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	211		192
Allowance for loan losses	211	208	192	96	97	94
Residential Real Estate Multi Family [Member] | Ending allowance attributed to loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	211		192
Residential Real Estate Multi Family [Member] | Ending loans balance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	16,033		15,559
Residential Real Estate Multi Family [Member] | Unallocated Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	0		0
Residential Real Estate Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	4		5
Allowance for loan losses	4	5	5	14	16	21
Residential Real Estate Construction [Member] | Ending allowance attributed to loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	4		5
Residential Real Estate Construction [Member] | Ending loans balance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	2,378		2,809
Residential Real Estate Construction [Member] | Unallocated Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	0		0
Land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	3		2
Allowance for loan losses	3	2	2	8	8	7
Land [Member] | Ending allowance attributed to loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	3		2
Land [Member] | Ending loans balance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	1,327		1,186
Land [Member] | Unallocated Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	0		0
Farm [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	4		3
Allowance for loan losses	4	4	3	9	9	9
Farm [Member] | Ending allowance attributed to loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	4		3
Farm [Member] | Ending loans balance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	1,955		1,735
Farm [Member] | Unallocated Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	0		0
Non residential real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment, Individually evaluated			0
Loans individually evaluated for impairment, Acquired with deteriorated credit quality			164
Loans individually evaluated for impairment, Total allowance			0
Loans collectively evaluated for impairment, Ending loans balance	230
Loans collectively evaluated for impairment, Total allowance			217
Non residential real estate [Member] | Ending allowance attributed to loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment, Ending loans balance			0
Loans collectively evaluated for impairment, Ending loans balance	230		217
Non residential real estate [Member] | Ending loans balance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment, Ending loans balance			164
Loans collectively evaluated for impairment, Ending loans balance	25,282		26,974
Non residential real estate [Member] | Unallocated Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment, Total allowance			0
Loans collectively evaluated for impairment, Ending loans balance	0
Loans collectively evaluated for impairment, Total allowance			0
Commercial Non-mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	4		18
Commercial Non-mortgage [Member] | Ending allowance attributed to loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	4		18
Commercial Non-mortgage [Member] | Ending loans balance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	2,308		1,847
Commercial Non-mortgage [Member] | Unallocated Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	0		0
Loans on deposits [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	3		4
Allowance for loan losses	3	4	4	11	13	13
Loans on deposits [Member] | Ending allowance attributed to loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	3		4
Loans on deposits [Member] | Ending loans balance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	1,741		1,813
Loans on deposits [Member] | Unallocated Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	0		0
Home equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	12		11
Allowance for loan losses	12	12	11	30	31	31
Home equity [Member] | Ending allowance attributed to loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	12		11
Home equity [Member] | Ending loans balance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	6,442		6,155
Home equity [Member] | Unallocated Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	0		0
Unsecured [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	1		1
Allowance for loan losses	1	1	1	2	2	3
Unsecured [Member] | Ending allowance attributed to loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	1		1
Unsecured [Member] | Ending loans balance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	372		552
Unsecured [Member] | Unallocated Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	0		0
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	200		200
Allowance for loan losses	200	200	200	200	200	200
Unallocated [Member] | Ending allowance attributed to loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	0		0
Unallocated [Member] | Ending loans balance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	0		0
Unallocated [Member] | Unallocated Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	200		200
Automobile [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	0		0
Allowance for loan losses	0	$ 0	0	$ 0	$ 0	$ 0
Automobile [Member] | Ending allowance attributed to loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	0		0
Automobile [Member] | Ending loans balance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Ending loans balance	46		69
Automobile [Member] | Unallocated Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment, Total allowance	$ 0		$ 0