Marketable Investment Securities (Tables)

6 Months Ended

Jun. 30, 2018

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. Certain of our investments in debt instruments and equity securities have experienced and are likely to continue to experience volatility.

	As of
	June 30, 2018		December 31, 2017
	(In thousands)
Marketable investment securities:
Debt securities:
Corporate bonds	$	1,168,020	$	542,573
Other debt securities	309,700		142,036
Total debt securities	1,477,720		684,609
Equity securities	172,119		139,571
Total marketable investment securities	1,649,839		824,180
Less: Restricted marketable investment securities	9,063		10,019
Total marketable investment securities	$	1,640,776	$	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 June 30, 2018
Corporate bonds	$	1,075,236	$	246	$	(306	)	$	1,075,176
Other debt securities	309,719		—		(19		)	309,700
Total available-for-sale debt securities	$	1,384,955	$	246	$	(325	)	$	1,384,876
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 June 30, 2018 and December 31, 2017, we did not have investments that were categorized within Level 3 of the fair value hierarchy.

	As of
	June 30, 2018						December 31, 2017
	Level 1		Level 2		Total		Level 1		Level 2		Total
	(In thousands)
Debt securities:
Corporate bonds	$	—	$	1,168,020	$	1,168,020	$	—	$	542,573	$	542,573
Other	10,400		299,300		309,700		13,311		128,725		142,036
Total debt securities	10,400		1,467,320		1,477,720		13,311		671,298		684,609
Equity securities	166,096		6,023		172,119		133,736		5,835		139,571
Total marketable investment securities	$	176,496	$	1,473,343	$	1,649,839	$	147,047	$	677,133	$	824,180