Short-term Investments (Tables)

9 Months Ended

Sep. 30, 2017

Short-Term Investments And Fair Value Measurement [Abstract]

Available-For-Sale Securities Reported at Fair Value

The following table summarizes, by major security type, the Company’s assets at December 31, 2016 that were measured at fair value, the category using the fair value hierarchy and where they are classified on the Consolidated Balance Sheets:

	As of December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value		Cash and cash equivalents		Short-term investments		Non-current assets (1)
	(in thousands)
Cash	$	1,267,523	$	—	$	—		$	1,267,523	$	1,264,126	$	—	$	3,397
Level 1 securities:
Money market funds	204,967		—		—			204,967		203,450		—		1,517
Level 2 securities:
Corporate debt securities	199,843		110		(731		)	199,222		—		199,222		—
Government securities	35,944		—		(128		)	35,816		—		35,816		—
Certificates of deposit	9,833		—		—			9,833		—		9,833		—
Agency securities	21,563		—		(228		)	21,335		—		21,335		—
Total	$	1,739,673	$	110	$	(1,087	)	$	1,738,696	$	1,467,576	$	266,206	$	4,914

(1) Primarily restricted cash that is related to workers compensation deposits and letter of credit agreements.