Convertible Senior Notes (Tables)

9 Months Ended

Sep. 30, 2017

Debt Disclosure [Abstract]

Schedule of Debt

The 2017 Notes consist of the following:

Liability component	September 30, 2017		December 31, 2016
	(in thousands)
Principal	$	—	$	55,000
Less: Debt discount, net(1)	—		(1,251		)
Net carrying amount	$	—	$	53,749

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⁽¹⁾  Included in the accompanying condensed consolidated balance sheets within convertible senior notes (due 2017) and amortized to interest expense over the remaining life of the 2017 Notes using the effective interest rate method.

The 2022 Notes consist of the following:

Liability component	September 30, 2017			December 31, 2016
	(in thousands)
Principal	$	399,997		$	400,000
Less: Debt discount, net(1)	(66,064		)	(75,754		)
Net carrying amount	$	333,933		$	324,246

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⁽¹⁾  Included in the accompanying condensed consolidated balance sheets within convertible senior notes (due 2022) and amortized to interest expense over the remaining life of the 2022 Notes using the effective interest rate method.

The 2023 Notes consist of the following:

Liability component	September 30, 2017			December 31, 2016
	(in thousands)
Principal	$	402,500		$	402,500
Less: Debt discount, net(1)	(93,778		)	(103,162		)
Net carrying amount	$	308,722		$	299,338

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⁽¹⁾  Included in the accompanying condensed consolidated balance sheets within convertible senior notes (due 2023) and amortized to interest expense over the remaining life of the 2023 Notes using the effective interest rate method.

Schedule of Interest Expense

The following table sets forth total interest expense recognized related to the 2023 Notes:

	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016
	(in thousands)						(in thousands)
Contractual interest expense	$	2,767		$	2,777		$	8,293		$	3,381
Amortization of debt discount	3,205			2,923			9,384			3,650
Total	$	5,972		$	5,700		$	17,677		$	7,031
Effective interest rate of the liability component	7.5		%	7.5		%	7.5		%	7.5		%

The following table sets forth total interest expense recognized related to the 2017 Notes:

	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016
	(in thousands)						(in thousands)
Contractual interest expense	$	—		$	189		$	315		$	1,912
Amortization of debt discount	—			621			1,251			6,699
Total	$	—		$	810		$	1,566		$	8,611
Effective interest rate of the liability component	6.02		%	6.02		%	6.02		%	6.02		%

The following table sets forth total interest expense recognized related to the 2022 Notes:

	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016
	(in thousands)						(in thousands)
Contractual interest expense	$	2,500		$	2,500		$	7,500		$	7,500
Amortization of debt discount	3,298			3,078			9,690			9,043
Total	$	5,798		$	5,578		$	17,190		$	16,543
Effective interest rate of the liability component	6.5		%	6.5		%	6.5		%	6.5		%