Summary of Quarterly Results of Operations (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Data [Abstract]

Summary of quarterly results of operations

	2017
	1st Quarter		2nd Quarter		3rd Quarter		4th Quarter		Full Year
Net sales	$	2,761,387	$	3,735,817	$	4,507,020	$	3,979,564	$	14,983,788
Gross profit	1,343,274		1,737,056		1,902,142		1,798,739		6,781,211
Net income	239,152		319,111		316,606		897,393		1,772,262
Net income per common share - basic	2.58		3.44		3.40		9.62		19.08
Net income per common share - diluted	2.53		3.36		3.33		9.39		18.67

	2016
	1st Quarter		2nd Quarter		3rd Quarter		4th Quarter		Full Year
Net sales	$	2,574,024	$	3,219,525	$	3,279,462	$	2,782,591	$	11,855,602
Gross profit	1,261,845		1,635,901		1,636,425		1,388,580		5,922,751
Net income	164,876		378,064		386,733		203,030		1,132,703
Net income per common share - basic	1.80		4.12		4.20		2.20		12.33
Net income per common share - diluted	1.75		3.99		4.08		2.15		11.99