Cash and Investments in Marketable Securities (Tables)

3 Months Ended

Mar. 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
	March 31, 2018		December 31, 2017
Cash and cash equivalents	$	34,805	$	4,762
Short-term investments		261,854		291,370
Long-term investments		37,157		57,088
Total cash and investments in marketable securities	$	333,816	$	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		March 31, 2018		December 31, 2017
Corporate notes and bonds		2	$	189,845	$	216,253
Corporate commercial paper		2		104,967		128,096
Obligations of U.S. government agencies		2		2,974		2,977
Available-for-sale investments				297,786		347,326
Money market funds		1		21,055		302
Certificate of deposit	N/A			1,225		1,132
Cash	N/A			13,750		4,460
Total cash and investments in marketable securities			$	333,816	$	353,220