Investments (Tables)

9 Months Ended

Sep. 30, 2018

Investments

Summary of available-for-sale securities

		September 30, 2018
			Gross		Gross
			Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
Corporate bonds:
U.S. corporations	$	6,418,761	$	—	$	100,558	$	6,318,203
International corporations		1,167,850		1,230		—		1,169,080
Total	$	7,586,611	$	1,230	$	100,558	$	7,487,283

		December 31, 2017
			Gross		Gross
			Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
Corporate bonds:
U.S. corporations	$	7,244,771	$	746	$	63,575	$	7,181,942
International corporations		971,087		707		18,613		953,181
Total	$	8,215,858	$	1,453	$	82,188	$	8,135,123