Consolidated Statements of Stockholders' Equity (Deficit) (Parentheticals) - shares shares in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock [Member]
Exercise of stock options, shares (in shares)	1,106		351
Employee stock purchase plan sales, shares (in shares)	92	95	75
Issuance of common stock, shares (in shares)	10,455	23,925

Number of share options (or share units) exercised during the current period.

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