Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Schedule of Marketable Securities [Table Text Block]

	2019						2018
	Cost		Unrealized Gains (Losses)		Fair Value		Cost		Unrealized Gains (Losses)		Fair Value
U.S. government securities	$	—	$	—	$	—	$	2	$	—	$	2
Corporate securities					—		4				4
Certificates of deposit	19				19		15				15
Total marketable securities	$	19	$	—	$	19	$	21	$	—	$	21