Marketable Securities

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

Marketable Securities

All of our marketable securities are classified as available-for-sale and consist of United States Treasury notes, which mature in 2019, and common stock. Below is a summary of our marketable securities as of December 31, 2017 (in thousands):

	December 31, 2017
	Cost or Amortized Cost		Unrealized Gain, Net		Estimated Fair Value
Marketable securities	$	276,567	$	361	$	276,928