Marketable Securities

6 Months Ended

Jun. 30, 2019

Investments, Debt and Equity Securities [Abstract]

Marketable Securities [Text Block]

Marketable Securities 

	June 30, 2019						December 31, 2018
	Cost		Unrealized Gain (Loss)		Fair Value		Cost		Unrealized Gain (Loss)		Fair Value
U.S. government securities	$	—	$	—	$	—	$	2	$	—	$	2
Corporate securities							4				4
Certificates of deposit	15				15		15				15
Total marketable securities	$	15	$	—	$	15	$	21	$	—	$	21

U.S. government securities include bonds issued by government-sponsored agencies and Treasury notes. Corporate securities are primarily debt securities. Certificates of deposit maturing in one year or less total $15 at June 30, 2019.