Cash and Investments in Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Cash and Investments in Marketable Securities, Including Cash Equivalents

Cash and investments in marketable securities, including cash equivalents, are as follows (in thousands):

	Estimated Fair Value at
	December 31, 2018		December 31, 2017
Cash and cash equivalents	$	194,905	$	4,762
Short-term investments		1,140,445		291,370
Long-term investments		582,889		57,088
Total cash and investments in marketable securities	$	1,918,239	$	353,220

Portfolio of Cash and Investments in Marketable Securities

Our portfolio of cash and investments in marketable securities includes (in thousands):

			Estimated Fair Value at
	Fair Value Hierarchy Level		December 31, 2018		December 31, 2017
Corporate notes and bonds		2	$	1,288,986	$	216,253
Corporate commercial paper		2		498,048		128,096
Obligations of U.S. government agencies		2		12,977		2,977
Available-for-sale investments				1,800,011		347,326
Money market funds		1		105,656		302
Certificate of deposit	N/A			6,760		1,132
Cash	N/A			5,812		4,460
Total cash and investments in marketable securities			$	1,918,239	$	353,220