5. Employee Benefit Plan (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Employee Benefit Plan Details Abstract
Service cost	$ 173,961	$ 157,968	$ 347,922	$ 315,936
Interest cost	121,802	113,224	243,604	226,448
Expected return on plan assets	(212,774)	(213,604)	(425,548)	(427,208)
Amortization of prior service cost	(3,809)	(3,809)	(7,618)	(7,618)
Amortization of net (gain) or loss	71,024	55,786	142,048	111,572
Net periodic pension cost	$ 150,204	$ 109,565	$ 300,408	$ 219,130