3. Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income	$ 7,971	$ 7,614	$ 27,947	$ 22,010
Weighted average basic shares outstanding	1,852	1,825	1,844	1,823
Add: Effect of dilutive securities	5	33	12	33
Weighted average diluted shares outstanding	1,857	1,858	1,856	1,856
Earnings per share:
Basic	$ 4.30	$ 4.17	$ 15.16	$ 12.07
Diluted	$ 4.29	$ 4.10	$ 15.06	$ 11.86