11. FAIR VALUE MEASUREMENTS - Assets and liabilities measured at fair value on recurring and non-recurring basis (Details 1) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Recurring
Impaired loans:
Total gain (losses)		$ 0
Non Recurring
Impaired loans:
Total gain (losses)	$ 0	(1,073)
US Government Agencies Debt Securities [Member]
Impaired loans:
Total gain (losses)		0
US Government Agencies Debt Securities [Member] | Fair Value
Available-for-sale securities:
Asset fair value disclosure recurring	250,290	232,869
US Government Agencies Debt Securities [Member] | Level 1
Available-for-sale securities:
Asset fair value disclosure recurring	0	0
US Government Agencies Debt Securities [Member] | Level 2
Available-for-sale securities:
Asset fair value disclosure recurring	250,290	232,869
US Government Agencies Debt Securities [Member] | Level 3
Available-for-sale securities:
Asset fair value disclosure recurring	0	0
Obligations of states and political subdivisions
Impaired loans:
Total gain (losses)		0
Obligations of states and political subdivisions | Fair Value
Available-for-sale securities:
Asset fair value disclosure recurring	15,541	22,715
Obligations of states and political subdivisions | Level 1
Available-for-sale securities:
Asset fair value disclosure recurring	0	0
Obligations of states and political subdivisions | Level 2
Available-for-sale securities:
Asset fair value disclosure recurring	15,541	22,715
Obligations of states and political subdivisions | Level 3
Available-for-sale securities:
Asset fair value disclosure recurring	0	0
Corporate bonds | Fair Value
Available-for-sale securities:
Asset fair value disclosure recurring	6,475
Corporate bonds | Level 1
Available-for-sale securities:
Asset fair value disclosure recurring	0
Corporate bonds | Level 2
Available-for-sale securities:
Asset fair value disclosure recurring	6,475
Corporate bonds | Level 3
Available-for-sale securities:
Asset fair value disclosure recurring	0
US Treasury securities | Fair Value
Available-for-sale securities:
Asset fair value disclosure recurring	4,963
US Treasury securities | Level 1
Available-for-sale securities:
Asset fair value disclosure recurring	4,963
US Treasury securities | Level 2
Available-for-sale securities:
Asset fair value disclosure recurring	0
US Treasury securities | Level 3
Available-for-sale securities:
Asset fair value disclosure recurring	0
Recurring | Fair Value
Available-for-sale securities:
Asset fair value disclosure recurring	277,269	262,322
Recurring | Level 1
Available-for-sale securities:
Asset fair value disclosure recurring	4,963	66
Recurring | Level 2
Available-for-sale securities:
Asset fair value disclosure recurring	272,306	262,256
Recurring | Level 3
Available-for-sale securities:
Asset fair value disclosure recurring	0	0
Commercial Loan [Member]
Impaired loans:
Total gain (losses)	0	(1,073)
Commercial Loan [Member] | Fair Value
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring	5,131	1,598
Commercial Loan [Member] | Level 1
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring	0	0
Commercial Loan [Member] | Level 2
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring	0	0
Commercial Loan [Member] | Level 3
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring	5,131	1,598
Land
Impaired loans:
Total gain (losses)	0	0
Land | Fair Value
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring	961	961
Land | Level 1
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring	0	0
Land | Level 2
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring	0	0
Land | Level 3
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring	961	961
Non Recurring | Fair Value
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring	6,902	3,066
Non Recurring | Level 1
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring	0	0
Non Recurring | Level 2
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring	0	0
Non Recurring | Level 3
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring	$ 6,902	3,066
Corporate Bonds
Impaired loans:
Total gain (losses)		0
Corporate Bonds | Fair Value
Available-for-sale securities:
Asset fair value disclosure recurring		6,626
Corporate Bonds | Level 1
Available-for-sale securities:
Asset fair value disclosure recurring		0
Corporate Bonds | Level 2
Available-for-sale securities:
Asset fair value disclosure recurring		6,626
Corporate Bonds | Level 3
Available-for-sale securities:
Asset fair value disclosure recurring		0
Corporate stock
Impaired loans:
Total gain (losses)		0
Corporate stock | Fair Value
Available-for-sale securities:
Asset fair value disclosure recurring		112
Corporate stock | Level 1
Available-for-sale securities:
Asset fair value disclosure recurring		66
Corporate stock | Level 2
Available-for-sale securities:
Asset fair value disclosure recurring		46
Corporate stock | Level 3
Available-for-sale securities:
Asset fair value disclosure recurring		0
Residential Real Estate [Member]
Impaired loans:
Total gain (losses)		0
Residential Real Estate [Member] | Fair Value
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring		329
Residential Real Estate [Member] | Level 1
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring		0
Residential Real Estate [Member] | Level 2
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring		0
Residential Real Estate [Member] | Level 3
Impaired loans:
Assets, Fair Value Disclosure, Nonrecurring		329
Real estate-commercial
Impaired loans:
Total gain (losses)		$ 0