12. Employee Benefits (Details - Fair value of plan assets) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair value of plan assets	$ 14,368	$ 16,446	$ 16,243
Level 1 [Member]
Fair value of plan assets	2,635	3,633
Level 2 [Member]
Fair value of plan assets	11,733	12,813
Level 3 [Member]
Fair value of plan assets	0	0
Company Common Stock [Member]
Fair value of plan assets	2,635	3,633
Company Common Stock [Member] \| Level 1 [Member]
Fair value of plan assets	2,635	3,633
Company Common Stock [Member] \| Level 2 [Member]
Fair value of plan assets	0	0
Company Common Stock [Member] \| Level 3 [Member]
Fair value of plan assets	0	0
Large Cap Value [Member]
Fair value of plan assets	1,983	2,324
Large Cap Value [Member] \| Level 1 [Member]
Fair value of plan assets	0	0
Large Cap Value [Member] \| Level 2 [Member]
Fair value of plan assets	1,983	2,324
Large Cap Value [Member] \| Level 3 [Member]
Fair value of plan assets	0	0
Mid Cap Index [Member]
Fair value of plan assets	563	654
Mid Cap Index [Member] \| Level 1 [Member]
Fair value of plan assets	0	0
Mid Cap Index [Member] \| Level 2 [Member]
Fair value of plan assets	563	654
Mid Cap Index [Member] \| Level 3 [Member]
Fair value of plan assets	0	0
Small Cap Growth [Member]
Fair value of plan assets	559	657
Small Cap Growth [Member] \| Level 1 [Member]
Fair value of plan assets	0	0
Small Cap Growth [Member] \| Level 2 [Member]
Fair value of plan assets	559	657
Small Cap Growth [Member] \| Level 3 [Member]
Fair value of plan assets	0	0
Small Cap Value [Member]
Fair value of plan assets	558	647
Small Cap Value [Member] \| Level 1 [Member]
Fair value of plan assets	0	0
Small Cap Value [Member] \| Level 2 [Member]
Fair value of plan assets	558	647
Small Cap Value [Member] \| Level 3 [Member]
Fair value of plan assets	0	0
Large Cap Blend [Member]
Fair value of plan assets	587	661
Large Cap Blend [Member] \| Level 1 [Member]
Fair value of plan assets	0	0
Large Cap Blend [Member] \| Level 2 [Member]
Fair value of plan assets	587	661
Large Cap Blend [Member] \| Level 3 [Member]
Fair value of plan assets	0	0
Growth [Member]
Fair value of plan assets	2,031	2,313
Growth [Member] \| Level 1 [Member]
Fair value of plan assets	0	0
Growth [Member] \| Level 2 [Member]
Fair value of plan assets	2,031	2,313
Growth [Member] \| Level 3 [Member]
Fair value of plan assets	0	0
International Growth [Member]
Fair value of plan assets	2,301	2,683
International Growth [Member] \| Level 1 [Member]
Fair value of plan assets	0	0
International Growth [Member] \| Level 2 [Member]
Fair value of plan assets	2,301	2,683
International Growth [Member] \| Level 3 [Member]
Fair value of plan assets	0	0
Core Bond [Member]
Fair value of plan assets	1,921	1,870
Core Bond [Member] \| Level 1 [Member]
Fair value of plan assets	0	0
Core Bond [Member] \| Level 2 [Member]
Fair value of plan assets	1,921	1,870
Core Bond [Member] \| Level 3 [Member]
Fair value of plan assets	0	0
High Yield [Member]
Fair value of plan assets	364	373
High Yield [Member] \| Level 1 [Member]
Fair value of plan assets	0	0
High Yield [Member] \| Level 2 [Member]
Fair value of plan assets	364	373
High Yield [Member] \| Level 3 [Member]
Fair value of plan assets	0	0
Inflation Protected Bond [Member]
Fair value of plan assets	510	505
Inflation Protected Bond [Member] \| Level 1 [Member]
Fair value of plan assets	0	0
Inflation Protected Bond [Member] \| Level 2 [Member]
Fair value of plan assets	510	505
Inflation Protected Bond [Member] \| Level 3 [Member]
Fair value of plan assets	0	0
Money Market [Member]
Fair value of plan assets	356	126
Money Market [Member] \| Level 1 [Member]
Fair value of plan assets	0	0
Money Market [Member] \| Level 2 [Member]
Fair value of plan assets	356	126
Money Market [Member] \| Level 3 [Member]
Fair value of plan assets	$ 0	$ 0