Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2019

Investments, Debt and Equity Securities [Abstract]

Schedule of Marketable Securities [Table Text Block]

	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