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Marketable Investment Securities (Tables)

9 Months Ended

Sep. 30, 2019

Marketable Investment Securities

Schedule of available-for-sale securities


					Gross			Gross
					unrealized			unrealized
		Amortized			holding			holding			Aggregate
September 30, 2019		Cost			gains			losses			fair value
Government bonds and notes		$	849,887		$	36		$	—		$	849,923
Corporate bonds, notes and commercial paper			4,030,728			225			—			4,030,953
		$	4,880,615		$	261		$	—		$	4,880,876


					Gross			Gross
					unrealized			unrealized
		Amortized			holding			holding			Aggregate
December 31, 2018		Cost			gains			losses			fair value
Government bonds and notes		$	897,481		$	—		$	(100)		$	897,381
Corporate bonds, notes and commercial paper			6,276,519			—			(863)			6,275,656
		$	7,174,000		$	—		$	(963)		$	7,173,037

Schedule of maturities of debt securities classified as available-for-sale securities


		Amortized			Aggregate
September 30, 2019		Cost			fair value
Due within one year		$	4,880,615		$	4,880,876