Cash and Investments in Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2019

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
	March 31, 2019		December 31, 2018
Cash and cash equivalents	$	106,752	$	194,905
Short-term investments		1,281,913		1,140,445
Long-term investments		455,867		582,889
Total cash and investments in marketable securities	$	1,844,532	$	1,918,239

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		March 31, 2019		December 31, 2018
Corporate notes and bonds		2	$	1,363,836	$	1,288,986
Corporate commercial paper		2		412,372		498,048
Obligations of U.S. government agencies		2		13,005		12,977
Available-for-sale investments				1,789,213		1,800,011
Money market funds		1		42,171		105,656
Certificate of deposit	N/A			6,759		6,760
Cash	N/A			6,389		5,812
Total cash and investments in marketable securities			$	1,844,532	$	1,918,239