Convertible Senior Notes (Tables)

6 Months Ended

Jun. 30, 2020

Debt Disclosure [Abstract]

Schedule of the Liability and Equity Components of the Convertible Senior Notes

The liability and equity components of the 2024 Notes consisted of the following (in thousands):

	As of June 30, 2020			As of December 31, 2019
	2024 Notes			2024 Notes
Liability component:
Principal	$	600,000		$	600,000
Less: 2024 Notes discounts and issuance costs, net of amortization	(105,063		)	(117,078		)
Net carrying amount	$	494,937		$	482,922
Equity component, net of issuance costs	$	138,064		$	138,064

The liability and equity components of the remaining portion of 2035 Notes consisted of the following (in thousands):

	As of June 30, 2020					As of December 31, 2019
	Series A Notes		Series B Notes			Series A Notes			Series B Notes
Liability component:
Principal	$	23,436	$	460,000		$	119,828		$	460,000
Less: 2035 Notes discount and issuance costs, net of amortization	—		(39,837		)	(2,540		)	(49,650		)
Net carrying amount	$	23,436	$	420,163		$	117,288		$	410,350
Equity component, net of issuance costs	$	15,559	$	117,834		$	79,555		$	117,834

Schedule of Interest Expense related to the Convertible Senior Notes

Interest expense for the three and six months ended June 30, 2020 related to the 2035 Notes consisted of the following (dollars in thousands):

	Three Months Ended June 30, 2020						Six Months Ended June 30, 2020
	Series A Notes			Series B Notes			Series A Notes			Series B Notes
Coupon interest	$	219		$	1,869		$	519		$	3,738
Amortization of 2035 Notes discount and issuance costs	1,023			4,935			2,540			9,812
Total interest expense recognized	$	1,242		$	6,804		$	3,059		$	13,550
Effective interest rate on the liability component	4.2		%	6.6		%	5.2		%	6.6		%

Interest expense for the three and six months ended June 30, 2019 related to the 2035 Notes consisted of the following (dollars in thousands):

	Three Months Ended June 30, 2019						Six Months Ended June 30, 2019
	Series A Notes			Series B Notes			Series A Notes			Series B Notes
Coupon interest	$	300		$	1,869		$	599		$	3,717
Amortization of 2035 Notes discount and issuance costs	1,460			4,707			2,902			9,359
Total interest expense recognized	$	1,760		$	6,576		$	3,501		$	13,076
Effective interest rate on the liability component	6.2		%	6.6		%	6.3		%	6.7		%

Interest expense related to the 2024 Notes consisted of the following (dollars in thousands):

	Three Months Ended June 30,						Six Months Ended June 30,
	2020			2019			2020			2019
	2024 Notes			2024 Notes			2024 Notes			2024 Notes
Coupon interest	$	1,313		$	1,313		$	2,625		$	2,625
Amortization of 2024 Notes discounts and issuance costs	6,044			5,754			12,015			11,438
Total interest expense recognized	$	7,357		$	7,067		$	14,640		$	14,063
Effective interest rate on the liability component	6.0		%	6.1		%	6.1		%	6.1		%