Consolidated Statements Stockholders' Equity (Deficit) (Unaudited) (Parentheticals) - shares shares in Thousands	3 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Common Stock [Member]
Exercise of stock options, shares (in shares)		100	160	200	226	242
Employee stock purchase plan sales, shares (in shares)	68		47	43		49
Issuance of common stock, shares (in shares)				10,455