Convertible Notes (Tables)

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Schedule of carrying value and unamortized discount on December 2021 Notes [Table Text Block]

The carrying value and unamortized discount of the December 2021 Notes were as follows:

(in thousands)	December 31, 2018			December 31, 2017
Principal amount of the December 2021 Notes	$	150,000		$	150,000
Unamortized discount of liability component	(25,356		)	(32,585		)
Net carrying value of the December 2021 Notes	$	124,644		$	117,415

Schedule of convertible and non-recourse notes activity

(in thousands)	February 2018 Notes			December 2021 Notes		Total
Balance at December 31, 2016	$	121,595		$	110,848	$	232,443
Amortization	4,471			6,567		11,038
Balance at December 31, 2017	126,066			117,415		243,481
Payment	(126,447		)	—		(126,447		)
Amortization	381			7,229		7,610
Balance at December 31, 2018	$	—		$	124,644	$	124,644

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

(in thousands)	December 2021 Notes		Total
2019	$	—	$	—
2020	—		—
2021	150,000		150,000
2022	—		—
2023	—		—
Thereafter	—		—
Total	$	150,000	$	150,000

Schedule of carrying value and unamortized discount on February 2018 Notes [Table Text Block]

The carrying value and unamortized discount of the February 2018 Notes were as follows:

(in thousands)	December 31, 2018		December 31, 2017
Principal amount of the February 2018 Notes	$	—	$	126,447
Unamortized discount of liability component	—		(381		)
Net carrying value of the February 2018 Notes	$	—	$	126,066

Schedule of interest expense for February 2018 Notes [Table Text Block]

Interest expense for the February 2018 Notes on the Company’s Consolidated Statements of Operations was as follows:

	Year Ended December 31,
(in thousands)	2018		2017		2016
Contractual coupon interest	$	422	$	5,058	$	9,338
Amortization of debt issuance costs	88		1,022		2,863
Amortization of debt discount	293		3,449		9,870
Total	$	803	$	9,529	$	22,071

Schedule of interest expense for December 2021 Notes [Table Text Block]

Interest expense for the December 2021 Notes on the Company’s Consolidated Statements of Operations was as follows:

	Year Ended December 31,
(in thousands)	2018		2017
Contractual coupon interest	$	4,125	$	4,125
Amortization of debt issuance costs	76		74
Amortization of debt discount	542		526
Amortization of conversion feature	6,611		5,967
Total	$	11,354	$	10,692