Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Summary of Fair Value Measured on Recurring Basis

The financial instrument that is measured at fair value on a recurring basis is summarized as follows as of December 31, 2017:

	(in thousands)
Assets	Level 1		Level 2		Level 3		December 31, 2017
Derivative embedded conversion feature	$	—	$	—	$	—	$	—

The financial instrument that is measured at fair value on a recurring basis is summarized as follows as of December 31, 2016:

	(in thousands)
Assets	Level 1		Level 2		Level 3		December 31, 2016
Derivative embedded conversion feature	$	—	$	—	$	80,651	$	80,651

Summary of Change in Level 3 Financial Instrument Measured at Fair Value on Recurring Basis

The following table shows the change in Level 3 financial instrument measured at fair value on a recurring basis for the period ended      December 31, 2017:

	Derivative asset (liability) embedded conversion feature (in thousands)
Balance, January 1, 2015	$	—
Issuance during 2015		(66,227	)
Loss on change in fair value		(54,621	)
Balance, December 31, 2015		(120,848	)
Gain on change in fair value		201,499
Balance, December 31, 2016		80,651
Gain on change in fair value		28,242
Reclassification of derivative asset		(108,893	)
Balance, December 31, 2017	$	—