Debt (Tables)

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Convertible Debt [Table Text Block]

Convertible senior notes consist of the following (in thousands):

	December 31, 2020						December 31, 2019
	Principal/ Fair Value Amount		Debt Issuance Costs		Net Amount		Principal/ Fair Value Amount		Debt Issuance Costs		Net Amount
4.875% convertible senior notes due 2020	$	—	$	—	$	—	$	1,905	$	—	$	1,905
3.25% convertible senior notes due 2023 *		34,134		—		34,134		50,753		—		50,753
Total convertible senior notes	$	34,134	$	—	$	34,134	$	52,658	$	—	$	52,658

Schedule of Long-term Debt Instruments [Table Text Block]

	Year ended December 31,
	2020		2019		2018
Contractual interest expense	$	—	$	—	$	373
Amortization of debt issuance costs recognized as interest expense		—		—		103
	$	—	$	—	$	476

	Year ended December 31,
	2020		2019		2018
Contractual interest expense	$	32	$	3,370	$	5,509
Amortization of debt issuance costs recognized as interest expense		—		460		789
	$	32	$	3,830	$	6,298

	Year ended December 31,
	2020		2019		2018
Contractual interest expense	$	—	$	580	$	815

	Year ended December 31,
	2020		2019		2018
Contractual interest expense	$	2,004	$	899	$	—

Schedule of Debt [Table Text Block]

Term loan consists of the following (in thousands):

	December 31, 2020							December 31, 2019
	Principal Amount**		Debt Discount/ Issuance Costs*			Net Amount		Principal Amount**		Debt Discount/ Issuance Costs*			Net Amount
Term Loan	$	119,801	$	(8,471	)	$	111,330	$	134,801	$	(12,319	)	$	122,482