Convertible debt (Tables)

12 Months Ended

Dec. 31, 2019

Debt Instrument [Line Items]

Convertible Debt [Table Text Block]

The Notes consist of the following (in thousands):

	December 31, 2019			December 31, 2018
Liability component:
Principal	$	143,750		$	250,000
Less: debt discount, net of amortization	(33,046		)	(24,810		)
Net carrying amount	$	110,704		$	225,190
Equity component (1)	$	32,883		$	37,560

(1) Recorded within additional paid-in capital in the Consolidated Balance Sheet. As of December 31, 2019, it included $32.9 million related to the 2024 Notes, net of $1.1 million issuance cost in equity, respectively. As of December 31, 2018, it included $28.7 million and $8.8 million related to the 2019 Notes and the 2047 Notes, respectively, net of $1.2 million and $0.3 million issuance cost in equity, respectively.

The following table sets forth total interest expense recognized related to the Notes (in thousands):

	Year Ended December 31,
	2019		2018
Coupon	$	3,691	$	5,000
Amortization of debt issuance costs	1,157		1,419
Amortization of debt discount	9,917		10,567
Total	$	14,765	$	16,986