Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2021

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

The following tables summarize the Company's financial liabilities measured at fair value on a recurring basis as of June 30, 2021 and December 31, 2020 (in thousands):

			Fair Value Measurements
			as of June 30, 2021
	Carrying Amount as of		Level 1		Level 2		Level 3
	June 30, 2021
3.25% convertible senior notes due in 2023	$	27,391	$	—	$	—	$	27,391
Preferred stock derivative liability		16,976		—		—		16,976

			Fair Value Measurements
			as of December 31, 2020
	Carrying Amount as of		Level 1		Level 2		Level 3
	December 31, 2020
3.25% convertible senior notes due in 2023	$	34,134	$	—	$	—	$	34,134
Preferred stock derivative liability		8,062		—		—		8,062

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

The following tables provide a reconciliation of the beginning and ending balances of liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) (in thousands):

3.25% convertible senior notes due in 2023	2021			2020
Balance, January 1,	$	34,134		$	50,753
Conversion of convertible senior notes		(19,872	)		(9,473	)
Change in fair value		12,844			52
PIK interest		285			925
Balance, June 30,	$	27,391		$	42,257

Preferred stock derivative liability	2021		2020
Balance, January 1,	$	8,062	$	5,247
Change in fair value		8,914		(2,083	)
Balance, June 30,	$	16,976	$	3,164