Debt - 2.5% Convertible Notes (Details)		9 Months Ended
	Feb. 14, 2014 USD ($)	Sep. 30, 2016 USD ($) day $ / shares	Dec. 31, 2015 USD ($)	Feb. 28, 2014 USD ($)
Debt Instrument [Line Items]
Carrying value		$ 177,146,000	$ 170,749,000
Convertible 2.5% notes
Debt Instrument [Line Items]
Aggregate principal amount of debt issued				$ 200,000,000
Net proceeds from issuance of convertible debt	$ 193,300,000
Fees and expenses	6,700,000
Proceeds used to pay the cost of the bond hedges (after such cost was partially offset by proceeds from the sale of warrants)	$ 14,100,000
Interest rate (as a percent)	2.50%
Initial conversion rate of common stock per $1000 of principal amount of Notes (in shares)		0.0369079
Principal amount used for debt instrument conversion ratio		$ 1,000
Initial conversion price of convertible notes into common stock (in usd per share) | $ / shares		$ 27.09
Number of consecutive trading days during which the closing price of the entity's common stock must exceed or equal the conversion price for at least 20 days in order for the notes to be convertible		30 days
Debt issuance costs allocated to equity component	$ 1,300,000
Debt issuance costs allocated to the liability component	5,400,000
Period of amortization of debt discount to interest expense using effective interest method		5 years
Debt term		5 years
Principal amount of debt outstanding		$ 199,998,000
Carrying value		$ 177,146,000
Effective interest rate on liability component (as a percent)		7.23%
Convertible 2.5% notes | Debt Instrument Convertible Covenant One
Debt Instrument [Line Items]
Number of days during 30 consecutive trading days in which the closing price of the entity's common stock must exceed or equal the conversion price for the notes to be convertible | day		20
Number of consecutive trading days during which the closing price of the entity's common stock must exceed or equal the conversion price for at least 20 days in order for the notes to be convertible		30 days
Convertible 2.5% notes | Debt Instrument Convertible Covenant One | Minimum
Debt Instrument [Line Items]
Percentage of the closing sales price of the entity's common stock that the conversion price must exceed or be equal in order for the notes to be convertible		130.00%
Convertible 2.5% notes | Debt Instrument Convertible Covenant Two
Debt Instrument [Line Items]
Principal amount used for debt instrument conversion ratio		$ 1,000
Number of consecutive business days after any five consecutive trading day period during the note measurement period		5 days
Number of consecutive trading days before five consecutive business days during the note measurement period		5 days
Convertible 2.5% notes | Debt Instrument Convertible Covenant Two | Maximum
Debt Instrument [Line Items]
Percentage of product of the last reported sale price of the entity's common stock and the conversion rate of convertible debt instruments (less than)		98.00%
Convertible 2.5% notes, net
Debt Instrument [Line Items]
Aggregate principal amount of debt issued	$ 200,000,000	$ 200,000,000.0
Interest rate (as a percent)		2.50%	2.50%
Principal amount of debt outstanding		$ 200,000,000