Borrowings (Tables)

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Summary of Borrowings

Borrowings consist of the following (in thousands):

	December 31,
	2018			2017
Facility Financing Obligation (2019 Notes and    Tranche B Notes)
Principal amount	$	11,495		$	54,407
Unamortized debt issuance costs and debt discount		(197	)		(1,662	)
Net carrying amount	$	11,298		$	52,745
Senior Convertible Notes (2021 Notes)
Principal amount	$	18,690		$	23,690
Unamortized premium		409			721
Net carrying amount	$	19,099		$	24,411
Note payable to related party - net carrying    amount	$	72,089		$	79,666

Accretion of Debt Issuance Cost and Debt Discount

Accretion of debt issuance cost and debt discount in connection with the Facility Agreement does not include the acceleration of the debt discount and issuance costs related to the transactions disclosed above as the amounts were included in the loss on extinguishment of debt in the consolidated statement of operations. Accretion of debt issuance cost and debt discount during the years ended December 31, 2018, 2017 and 2016 were as follows (in thousands):

	December 31,
	2018		2017		2016
Accretion expense - debt issuance cost	$	46	$	31		35
Accretion expense - debt discount	$	1,155	$	1,700		1,722

Schedule of Amortization of Premium and Accretion of Debt Issuance Costs

Amortization of the premium and accretion of debt issuance costs related to the 2021 notes for the years ended December 31, 2018, 2017 and 2016 are as follows (in thousands):

	December 31,
	2018		2017		2016
Amortization of debt premium	$	154	$	232		234
Accretion expense - debt issuance cost	$	4	$	227		257