Cash and Investments in Marketable Securities (Tables)

6 Months Ended

Jun. 30, 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
	June 30, 2018		December 31, 2017
Cash and cash equivalents	$	911,125	$	4,762
Short-term investments		912,683		291,370
Long-term investments		282,277		57,088
Total cash and investments in marketable securities	$	2,106,085	$	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		June 30, 2018		December 31, 2017
Corporate commercial paper		2	$	1,201,026	$	128,096
Corporate notes and bonds		2		671,323		216,253
Obligations of U.S. government agencies		2		123,972		2,977
Available-for-sale investments				1,996,321		347,326
Money market funds		1		100,299		302
Certificate of deposit	N/A			6,713		1,132
Cash	N/A			2,752		4,460
Total cash and investments in marketable securities			$	2,106,085	$	353,220