Loans Receivable and Allowance for Loan Losses, Loans modified as TDRs (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) loan contract	Sep. 30, 2017 loan contract	Sep. 30, 2018 USD ($) loan contract	Sep. 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	44		44		50
Accrual status | $	$ 11,271		$ 11,271		$ 13,714
Number of modifications	4		4		4
Nonaccrual status | $	$ 997		$ 997		$ 820
Total number of modifications	48		48		54
Total balance of modifications | $	$ 12,268		$ 12,268		$ 14,534
Number of contract, subsequent defaults	0	0	0	0
Residential Mortgage [Member]
TDRs loans accounted under method [Abstract]
Number of modifications	38		38		42
Accrual status | $	$ 10,031		$ 10,031		$ 11,631
Number of modifications	4		4		2
Nonaccrual status | $	$ 997		$ 997		$ 736
Total number of modifications	42		42		44
Total balance of modifications | $	$ 11,028		$ 11,028		$ 12,367
Commercial Real Estate [Member]
TDRs loans accounted under method [Abstract]
Number of modifications	2		2		3
Accrual status | $	$ 1,028		$ 1,028		$ 1,862
Number of modifications					1
Nonaccrual status | $					$ 78
Total number of modifications	2		2		4
Total balance of modifications | $	$ 1,028		$ 1,028		$ 1,940
ADC [Member]
TDRs loans accounted under method [Abstract]
Number of modifications	1		1		1
Accrual status | $	$ 134		$ 134		$ 137
Number of modifications					1
Nonaccrual status | $					$ 6
Total number of modifications	1		1		2
Total balance of modifications | $	$ 134		$ 134		$ 143
Consumer [Member]
TDRs loans accounted under method [Abstract]
Number of modifications	3		3		4
Accrual status | $	$ 78		$ 78		$ 84
Total number of modifications	3		3		4
Total balance of modifications | $	$ 78		$ 78		$ 84