Debt (Tables)

3 Months Ended

Mar. 31, 2019

Debt Disclosure [Abstract]

Schedule of Long-term Debt

The Notes consisted of the following:

	March 31, 2019			December 31, 2018
Principal	$	143,750		$	143,750
Less: debt discount, net of amortization	(25,307		)	(26,636		)
Less: debt issuance costs, net of amortization	(3,349		)	(3,528		)
Net carrying amount of the Notes	$	115,094		$	113,586

The total estimated fair value of the Notes as of March 31, 2019 and December 31, 2018 was approximately $138,998 and $117,875, respectively, based on the closing trading price of the Notes on last day of trading for the period. The fair value has been classified as Level 2 within the fair value hierarchy given the limited trading activity of the Notes.

The following table sets forth total interest expense recognized related to the Notes for the period presented:

	Three months ended March 31, 2019
Amortization of debt discount	$	1,329
Amortization of debt issuance costs	178
Total amortization of debt issuance costs and accretion of equity portion	1,507
Contractual interest expense	629
Total interest expense related to the Notes	$	2,136
Effective interest rate of the liability component	7.25		%