Debt (Tables)
 9 Months Ended
Sep. 30, 2016
Debt Disclosure [Abstract]  
Outstanding Convertible Debt and Related Deferred Financing Costs
The following table shows the gross and net carrying amount of the Company's convertible debt (in thousands): 
 
September 30,
2016
 
December 31, 2015
Principal amount of the 2% Convertible Senior Notes
$
67,084

 
$
201,250

Principal amount of the 1.25% Convertible Senior Notes
345,000

 
—

Unamortized debt discount
(73,148
)
 
(25,704
)
Deferred financing costs
(9,974
)
 
(3,848
)
Long-term debt, net carrying amount
$
328,962

 
$
171,698
Interest and Other Expense
Interest expense related to the 2% Notes and the 1.25% Notes was as follows (in thousands): 
 
Three Months Ended September 30,
 
Nine Months Ended September 30,
 
2016
 
2015
 
2016
 
2015
Contractual coupon interest
$
1,041

 
$
1,007

 
$
3,054

 
$
3,019

Amortization of debt discount
1,901

 
1,650

 
5,330

 
4,876

Amortization of debt issuance costs
222

 
281

 
785

 
844

Total interest expense from the Notes
$
3,164

 
$
2,938

 
$
9,169

 
$
8,739