Marketable Investment Securities (Tables)

12 Months Ended

Dec. 31, 2018

Investments [Abstract]

Schedule of Investments

Our marketable investment securities portfolio consists of various debt and equity instruments summarized in the table below. Certain of our investments in debt and equity instruments have historically experienced and are likely to continue experiencing volatility.

	As of December 31,
	2018		2017
	(In thousands)
Marketable investment securities:
Debt securities:
Corporate bonds	$	1,735,653	$	542,573
Other debt securities	464,997		142,036
Total debt securities	2,200,650		684,609
Equity securities	90,976		139,571
Total marketable investment securities	2,291,626		824,180
Less: Restricted marketable investment securities	9,474		10,019
Total marketable investment securities - current	$	2,282,152	$	814,161

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.

	Amortized		Unrealized					Estimated
	Cost		Gains		Losses			Fair Value
	(In thousands)
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
As of December 31, 2017
Corporate bonds	$	542,861	$	—	$	(288	)	$	542,573
Other debt securities	142,082		—		(46		)	142,036
Total available-for-sale debt securities	$	684,943	$	—	$	(334	)	$	684,609

Schedule of Fair Value Measurements

Our marketable investment securities are measured at fair value on a recurring basis as summarized in the table below. As of December 31, 2018 and 2017, we did not have investments that were categorized within Level 3 of the fair value hierarchy.

	As of December 31,
	2018						2017
	Level 1		Level 2		Total		Level 1		Level 2		Total
	(In thousands)
Debt securities:
Corporate bonds	$	—	$	1,735,653	$	1,735,653	$	—	$	542,573	$	542,573
Other debt securities	9,474		455,523		464,997		13,311		128,725		142,036
Total debt securities	9,474		2,191,176		2,200,650		13,311		671,298		684,609
Equity securities	85,298		5,678		90,976		133,736		5,835		139,571
Total marketable investment securities	$	94,772	$	2,196,854	$	2,291,626	$	147,047	$	677,133	$	824,180