Marketable Investment Securities (Tables)

9 Months Ended

Sep. 30, 2019

Investments, Debt and Equity Securities [Abstract]

Schedule of marketable investment securities

Our marketable investment securities portfolio consists of various debt and equity instruments summarized in the table below (amounts in thousands):

	As of
	September 30, 2019		December 31, 2018
Marketable investment securities:
Debt securities:
Corporate bonds	$	758,654	$	1,735,653
Other debt securities	216,958		464,997
Total debt securities	975,612		2,200,650
Equity securities	35,332		90,976
Total marketable investment securities	1,010,944		2,291,626
Less: Restricted marketable investment securities	10,779		9,474
Total marketable investment securities	$	1,000,165	$	2,282,152

Schedule of unrealized gains (losses) on available-for-sale securities

A summary of our available-for-sale debt securities, exclusive of securities where we have elected the fair value option, is presented in the table below (amounts in thousands):

	Amortized		Unrealized					Estimated
	Cost		Gains		Losses			Fair Value
As of September 30, 2019
Corporate bonds	$	748,815	$	1,150	$	(6	)	$	749,959
Other debt securities	216,943		15		—			216,958
Total available-for-sale debt securities	$	965,758	$	1,165	$	(6	)	$	966,917
As of December 31, 2018
Corporate bonds	$	1,689,093	$	318	$	(1,896	)	$	1,687,515
Other debt securities	464,993		7		(3		)	464,997
Total available-for-sale debt securities	$	2,154,086	$	325	$	(1,899	)	$	2,152,512

Schedule of fair value measurements

Our marketable investment securities are measured at fair value on a recurring basis as summarized in the table below (amounts in thousands). Certain of our investments in debt and equity instruments have historically experienced and are likely to continue experiencing volatility. As of September 30, 2019 and December 31, 2018, we did not have investments that were categorized within Level 3 of the fair value hierarchy.

	As of
	September 30, 2019						December 31, 2018
	Level 1		Level 2		Total		Level 1		Level 2		Total
Debt securities:
Corporate bonds	$	—	$	758,654	$	758,654	$	—	$	1,735,653	$	1,735,653
Other debt securities	10,779		206,179		216,958		9,474		455,523		464,997
Total debt securities	10,779		964,833		975,612		9,474		2,191,176		2,200,650
Equity securities	28,521		6,811		35,332		85,298		5,678		90,976
Total marketable investment securities	$	39,300	$	971,644	$	1,010,944	$	94,772	$	2,196,854	$	2,291,626