Cash and Investments in Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Cash and Investments in Marketable Securities, Including Cash Equivalents and Restricted Cash

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

	Estimated Fair Value at
	December 31, 2016		December 31, 2015
Cash and cash equivalents	$	59,640	$	55,570
Short-term investments		329,462		253,374
Total cash and investments in marketable securities	$	389,102	$	308,944

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, 2016		December 31, 2015
Corporate commercial paper		2	$	160,920	$	61,150
Corporate notes and bonds		2		156,044		181,969
Obligations of U.S. government agencies		2		13,749		7,325
Available-for-sale investments				330,713		250,444
Money market funds		1		51,104		53,728
Certificate of deposit	N/A			2,930		2,930
Cash	N/A			4,355		1,842
Total cash and investments in marketable securities			$	389,102	$	308,944