Debt (Tables)

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Schedule of outstanding debt obligations

Our outstanding debt obligations as of December 31, 2018 and December 31, 2017 consisted of the following (in thousands):

	December 31,
	2018		2017
2023 Senior Notes	$	—	$	466,291
2022 Convertible Notes	261,933		248,194
2019 Convertible Notes	21,276		20,198
Total long-term debt	283,209		734,683
Less: current maturities	21,276		—
Long-term debt, net of current maturities	$	261,933	$	734,683

Schedule of outstanding convertible debt

The outstanding balances of our Convertible Notes as of December 31, 2018 consisted of the following (in thousands):

	2022 Convertible Notes		2019 Convertible Notes		Total
Liability component:
Principal	$	320,000	$	21,417	$	341,417
Less: debt discount and issuance costs, net	58,067		141		58,208
Net carrying amount	$	261,933	$	21,276	$	283,209
Gross equity component	$	72,576	$	9,905	$	82,481

Schedule of total interest expense recognized related to the convertible notes

The following table sets forth total interest expense recognized related to the Convertible Notes during 2018, 2017, and 2016 (in thousands):

	Years Ended December 31,
	2018		2017		2016
Contractual interest expense	$	10,935	$	8,961	$	5,000
Amortization of debt issuance costs	1,403		1,275		1,072
Amortization of debt discount	13,414		11,071		7,544
Total interest expense	$	25,752	$	21,307	$	13,616

Schedule of maturities of long-term debt

Future annual principal payments on our long-term debt as of December 31, 2018 were as follows (in thousands):

Period	Future Annual Principal Payments
Year Ending December 31, 2019	$	21,417
Year Ending December 31, 2020	—
Year Ending December 31, 2021	—
Year Ending December 31, 2022	320,000
Thereafter	—
Total	$	341,417