Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2018

Stockholders' Equity Note [Abstract]

Schedule of Convertible Preferred Stock [Table Text Block]

	Shares authorized	Shares outstanding	Net carrying value		Liquidation preference
			(in thousands)		(in thousands)
Series A	94,988	94,988	$	2,949	$	2,737
Series B	747,095	520,973		16,115		17,219
Series C	820,088	605,103		19,877		20,000
Total	1,662,171	1,221,064	$	38,941	$	39,956

Schedule of Common Stock Reserved for Issuance [Table Text Block]

	March 31, 2018	December 31, 2017
Convertible preferred stock outstanding	—	1,221,064
Options issued and outstanding	832,942	304,850
Available for future grants of equity awards	380,426	—
Cumulative convertible preferred stock dividends	—	441,096
Convertible preferred stock warrants	10,914	10,914
Total	1,224,282	1,977,924