Marketable Investment Securities

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

MARKETABLE INVESTMENT SECURITIES

MARKETABLE INVESTMENT SECURITIES

The following table presents our Marketable investment securities:

	As of
	March 31, 2020			December 31, 2019
Marketable investment securities:
Debt securities:
Available-for-sale:
Corporate bonds	$	446,515		$	568,442
Other debt securities	303,703			335,580
Total available-for-sale debt securities	750,218			904,022
Fair value option - corporate bonds	12,181			9,128
Total debt securities	762,399			913,150
Equity securities	29,673			35,566
Total marketable investment securities, including restricted amounts	792,072			948,716
Less: Restricted marketable investment securities	(1,711		)	(8,093		)
Total marketable investment securities	$	790,361		$	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 March 31, 2020
Corporate bonds	$	449,483	$	—	$	(2,968	)	$	446,515
Other debt securities	303,694		9		—			303,703
Total available-for-sale debt securities	$	753,177	$	9	$	(2,968	)	$	750,218
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 March 31,
	2020		2019
Proceeds from sales	$	10,000	$	435,978
Gains (losses) on sales, net	$	—	$	549

As of March 31, 2020, we have $705.7 million of available-for-sale debt securities with contractual maturities of one year or less and $44.5 million with contractual maturities greater than one year.

Fair Value Option

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

	For the three months ended March 31,
	2020			2019
Gains (losses) on investments, net	$	(4,208	)	$	4,198

For the three months ended March 31, 2020 and 2019, we did not have any sales of fair value option corporate bonds.

Equity Securities

The following table presents the activity of our equity securities:

	For the three months ended March 31,
	2020			2019
Proceeds from sales	$	134		$	50,877
Gains (losses) on investments, net	$	(11,115	)	$	30,249

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
	March 31, 2020								December 31, 2019
	Level 1			Level 2		Total			Level 1			Level 2		Total
Debt securities:
Available-for-sale:
Corporate bonds	$	—		$	446,515	$	446,515		$	—		$	568,442	$	568,442
Other debt securities	1,711			301,992		303,703			8,093			327,487		335,580
Total available-for-sale debt securities	1,711			748,507		750,218			8,093			895,929		904,022
Fair value option - corporate bonds	—			12,181		12,181			—			9,128		9,128
Total debt securities	1,711			760,688		762,399			8,093			905,057		913,150
Equity securities	23,090			6,583		29,673			27,933			7,633		35,566
Total marketable investment securities, including restricted amounts	24,801			767,271		792,072			36,026			912,690		948,716
Less: Restricted marketable investment securities	(1,711		)	—		(1,711		)	(8,093		)	—		(8,093		)
Total marketable investment securities	$	23,090		$	767,271	$	790,361		$	27,933		$	912,690	$	940,623

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