Convertible Senior Notes (Tables)

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Schedule of Components of Convertible Senior Notes

The Notes consist of the following (in thousands):

	Year Ended December 31,
	2018			2017
Liability component:
Principal	$	115,000		$	115,000
Less: debt discount, net of amortization		(20,903	)		(25,519	)
Net carrying amount	$	94,097		$	89,481
Equity component (a)		22,094			22,094

(a) Recorded in the consolidated balance sheet within additional paid-in capital, net of $0.8 million transaction costs in equity.

Summary of Total Interest Expense Recognized Related To Convertible Senior Notes

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

	Year Ended December 31,
	2018		2017
1.50% coupon	$	1,725	$	192
Amortization of debt discount and transaction costs		4,616		499
	$	6,341	$	691

Summary of Fair Value and Carrying Value of Convertible Senior Notes

As of December 31, 2018, the fair value of the Notes, which was determined based on inputs that are observable in the market or that could be derived from, or corroborated with, observable market data, quoted price of the Notes in an over-the-counter market (Level 2), and carrying value of debt instruments (carrying value excludes the equity component of the Company’s convertible notes classified in equity) were as follows (in thousands):

	December 31, 2018				December 31, 2017
	Fair Value		Carrying Value		Fair Value		Carrying Value
Convertible senior notes	$	189,802	$	94,097	$	126,931	$	89,481