Marketable Investment Securities

6 Months Ended

Jun. 30, 2020

Investments, Debt and Equity Securities [Abstract]

The following table presents our Marketable investment securities:


	As of
	June 30, 2020		December 31, 2019
Marketable investment securities:
Debt securities:
Available-for-sale:
Corporate bonds	$	381,201	$	568,442
Other debt securities	89,924		335,580
Total available-for-sale debt securities	471,125		904,022
Fair value option - corporate bonds	12,038		9,128
Total debt securities	483,163		913,150
Equity securities	27,548		35,566
Total marketable investment securities, including restricted amounts	510,711		948,716
Less: Restricted marketable investment securities	(731)		(8,093)
Total marketable investment securities	$	509,980	$	940,623

Debt Securities

Our corporate bond portfolio includes debt instruments issued by individual corporations, primarily in the industrial and financial services industries. Our other debt securities portfolio includes investments in various debt instruments, including U.S. government bonds, commercial paper and mutual funds.

Available-for-Sale

The following table presents the components of our available-for-sale debt securities:


	Amortized		Unrealized						Estimated
	Cost		Gains		Losses		Fair Value
As of June 30, 2020
Corporate bonds	$	381,071	$	132	$	(2)	$	381,201
Other debt securities	89,923		1		—		89,924
Total available-for-sale debt securities	$	470,994	$	133	$	(2)	$	471,125

As of December 31, 2019
Corporate bonds	$	567,926	$	518	$	(2)	$	568,442
Other debt securities	335,572		8		—		335,580
Total available-for-sale debt securities	$	903,498	$	526	$	(2)	$	904,022

The following table presents the activity on our available-for-sale debt securities:


	For the three months ended June 30,						For the six months ended June 30,
	2020		2019		2020		2019
Proceeds from sales	$	—	$	—	$	10,000	$	435,978




Gains (losses) on sales, net	$	—	$	—	$	—	$	549

As of June 30, 2020, all $471.1 million of our available-for-sale debt securities had contractual maturities of one year or less.

Fair Value Option

The following table presents the activity on our fair value option corporate bonds:


	For the three months ended June 30,						For the six months ended June 30,
	2020		2019		2020		2019
Proceeds from sales	$	—	$	46,717	$	—	$	46,717
Gains (losses) on investments, net	$	(298)	$	224	$	(4,506)	$	4,422

Equity Securities

The following table presents the activity of our equity securities:


	For the three months ended June 30,						For the six months ended June 30,
	2020		2019		2020		2019
Proceeds from sales	$	4,719	$	29,051	$	4,853	$	79,928
Gains (losses) on investments, net	$	2,512	$	13,028	$	(8,603)	$	43,277

Fair Value Measurements

The following table presents our marketable investment securities categorized by the fair value hierarchy, certain of which have historically experienced volatility:


	As of
	June 30, 2020										December 31, 2019
	Level 1		Level 2		Total		Level 1		Level 2		Total
Debt securities:
Available-for-sale:
Corporate bonds	$	—	$	381,201	$	381,201	$	—	$	568,442	$	568,442
Other debt securities	731		89,193		89,924		8,093		327,487		335,580
Total available-for-sale debt securities	731		470,394		471,125		8,093		895,929		904,022
Fair value option - corporate bonds	—		12,038		12,038		—		9,128		9,128
Total debt securities	731		482,432		483,163		8,093		905,057		913,150
Equity securities	19,872		7,676		27,548		27,933		7,633		35,566
Total marketable investment securities, including restricted amounts	20,603		490,108		510,711		36,026		912,690		948,716
Less: Restricted marketable investment securities	(731)		—		(731)		(8,093)		—		(8,093)
Total marketable investment securities	$	19,872	$	490,108	$	509,980	$	27,933	$	912,690	$	940,623

As of June 30, 2020 and December 31, 2019, we did not have any investments that were categorized within Level 3 of the fair value hierarchy.