Loans Receivable and Allowance for Loan Losses, Loans modified as TDRs (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($) loan contract	Jun. 30, 2017 loan contract	Jun. 30, 2018 USD ($) loan contract	Jun. 30, 2017 loan contract	Dec. 31, 2017 USD ($) contract
Loans modified [Abstract]
Number of modifications | loan	0	0	0	0
TDRs loans accounted under method [Abstract]
Number of modifications	46		46		50
Accrual status | $	$ 11,868		$ 11,868		$ 13,714
Number of modifications	4		4		4
Nonaccrual status | $	$ 803		$ 803		$ 820
Total number of modifications	50		50		54
Total balance of modifications | $	$ 12,671		$ 12,671		$ 14,534
Number of contract, subsequent defaults	0	0	0	0
Residential Mortgage [Member]
TDRs loans accounted under method [Abstract]
Number of modifications	40		40		42
Accrual status | $	$ 10,617		$ 10,617		$ 11,631
Number of modifications	4		4		2
Nonaccrual status | $	$ 803		$ 803		$ 736
Total number of modifications	44		44		44
Total balance of modifications | $	$ 11,420		$ 11,420		$ 12,367
Commercial Real Estate [Member]
TDRs loans accounted under method [Abstract]
Number of modifications	2		2		3
Accrual status | $	$ 1,036		$ 1,036		$ 1,862
Number of modifications					1
Nonaccrual status | $					$ 78
Total number of modifications	2		2		4
Total balance of modifications | $	$ 1,036		$ 1,036		$ 1,940
ADC [Member]
TDRs loans accounted under method [Abstract]
Number of modifications	1		1		1
Accrual status | $	$ 135		$ 135		$ 137
Number of modifications					1
Nonaccrual status | $					$ 6
Total number of modifications	1		1		2
Total balance of modifications | $	$ 135		$ 135		$ 143
Consumer [Member]
TDRs loans accounted under method [Abstract]
Number of modifications	3		3		4
Accrual status | $	$ 80		$ 80		$ 84
Total number of modifications	3		3		4
Total balance of modifications | $	$ 80		$ 80		$ 84