Marketable Investment Securities (Tables)

9 Months Ended

Sep. 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 as follows:

	As of
	September 30, 2018		December 31, 2017
	(In thousands)
Marketable investment securities:
Debt securities:
Corporate bonds	$	1,028,521	$	368,083
Other debt securities	172,612		86,417
Total debt securities	1,201,133		454,500
Equity securities	1,357		1,102
Total marketable investment securities	$	1,202,490	$	455,602

Schedule of unrealized gains (losses) on marketable investment securities

	Amortized		Unrealized					Estimated
	Cost		Gains		Losses			Fair Value
	(In thousands)
As of September 30, 2018
Corporate bonds	$	1,028,554	$	502	$	(535	)	$	1,028,521
Other debt securities	172,612		—		—			172,612
Total available-for-sale debt securities	$	1,201,166	$	502	$	(535	)	$	1,201,133
As of December 31, 2017
Corporate bonds	$	368,291	$	—	$	(208	)	$	368,083
Other debt securities	86,425		—		(8		)	86,417
Total available-for-sale debt securities	$	454,716	$	—	$	(216	)	$	454,500

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 September 30, 2018 and December 31, 2017, we did not have investments that were categorized within Level 3 of the fair value hierarchy.

	As of
	September 30, 2018						December 31, 2017
	Level 1		Level 2		Total		Level 1		Level 2		Total
	(In thousands)
Debt securities:
Corporate bonds	$	—	$	1,028,521	$	1,028,521	$	—	$	368,083	$	368,083
Other	—		172,612		172,612		—		86,417		86,417
Total debt securities	—		1,201,133		1,201,133		—		454,500		454,500
Equity securities	1,357		—		1,357		1,102		—		1,102
Total marketable investment securities	$	1,357	$	1,201,133	$	1,202,490	$	1,102	$	454,500	$	455,602