(11) Employee Benefits (Details - Fair value of plan assets) - USD ($) $ in Thousands		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 18,165	$ 15,910	$ 14,368
Company Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		3,811	2,950
Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,523	2,370
Mid Cap Index [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		757	658
Small Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		765	655
Small Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		785	674
Large Cap Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		691	683
Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,342	2,342
International Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		3,003	2,667
Core Bond [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1,809	1,909
High Yield [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		381	386
Inflation Protected Bond [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		485	509
Money Market [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		813	107
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	3,811	2,950
Fair Value, Inputs, Level 1 [Member] | Company Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	3,811	2,950
Fair Value, Inputs, Level 1 [Member] | Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0	0
Fair Value, Inputs, Level 1 [Member] | Mid Cap Index [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0	0
Fair Value, Inputs, Level 1 [Member] | Small Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0	0
Fair Value, Inputs, Level 1 [Member] | Small Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0	0
Fair Value, Inputs, Level 1 [Member] | Large Cap Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0	0
Fair Value, Inputs, Level 1 [Member] | Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0	0
Fair Value, Inputs, Level 1 [Member] | International Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0	0
Fair Value, Inputs, Level 1 [Member] | Core Bond [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0	0
Fair Value, Inputs, Level 1 [Member] | High Yield [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0	0
Fair Value, Inputs, Level 1 [Member] | Inflation Protected Bond [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0	0
Fair Value, Inputs, Level 1 [Member] | Money Market [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0	0
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	14,354	12,960
Fair Value, Inputs, Level 2 [Member] | Company Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	0	0
Fair Value, Inputs, Level 2 [Member] | Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	2,523	2,370
Fair Value, Inputs, Level 2 [Member] | Mid Cap Index [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	757	658
Fair Value, Inputs, Level 2 [Member] | Small Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	765	655
Fair Value, Inputs, Level 2 [Member] | Small Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	785	674
Fair Value, Inputs, Level 2 [Member] | Large Cap Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	691	683
Fair Value, Inputs, Level 2 [Member] | Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	2,342	2,342
Fair Value, Inputs, Level 2 [Member] | International Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	3,003	2,667
Fair Value, Inputs, Level 2 [Member] | Core Bond [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	1,809	1,909
Fair Value, Inputs, Level 2 [Member] | High Yield [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	381	386
Fair Value, Inputs, Level 2 [Member] | Inflation Protected Bond [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	485	509
Fair Value, Inputs, Level 2 [Member] | Money Market [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	813	107
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0	0
Fair Value, Inputs, Level 3 [Member] | Company Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0	0
Fair Value, Inputs, Level 3 [Member] | Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0	0
Fair Value, Inputs, Level 3 [Member] | Mid Cap Index [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0	0
Fair Value, Inputs, Level 3 [Member] | Small Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0	0
Fair Value, Inputs, Level 3 [Member] | Small Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0	0
Fair Value, Inputs, Level 3 [Member] | Large Cap Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0	0
Fair Value, Inputs, Level 3 [Member] | Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0	0
Fair Value, Inputs, Level 3 [Member] | International Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0	0
Fair Value, Inputs, Level 3 [Member] | Core Bond [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0	0
Fair Value, Inputs, Level 3 [Member] | High Yield [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0	0
Fair Value, Inputs, Level 3 [Member] | Inflation Protected Bond [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0	0
Fair Value, Inputs, Level 3 [Member] | Money Market [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	$ 0	$ 0

[1] Company common stock is classified as level 1 and valued using quoted prices in active markets for identical assets.

[2] All other plan assets in stock, bond and money market funds are classified as level 2 and valued using significant observable inputs.

[3] There are no plan assets classified as level 3 in the fair value hierarchy as a result of having significant unobservable inputs.