15. OTHER NONINTEREST INCOME AND EXPENSE - Other noninterest income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income and Expenses [Abstract]
Merchant fee income	$ 411	$ 377	$ 378
Increase in cash surrender value of life insurance policies (Note 16)	317	322	316
Other	242	251	237
Other noninterest income	$ 970	$ 950	$ 931