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Convertible Senior Notes - Additional Information (Details) $ / shares in Units, shares in Millions		1 Months Ended		12 Months Ended
	May 02, 2017 USD ($) d $ / shares	Dec. 31, 2020 USD ($) shares	Nov. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Principal amount		$ 381,300,000		$ 381,300,000	$ 517,500,000
Equity component of repurchased convertible senior notes				47,500,000
Loss on extinguishment of convertible senior notes				$ 18,400,000	0	$ 0
2.25% Convertible senior notes due 2024
Debt Instrument [Line Items]
Principal amount	$ 517,500,000
Stated interest rate percentage	2.25%
Proceeds from issuance	$ 502,800,000
Threshold common stock trading days | d	20
Threshold consecutive common stock trading days | d	30
Threshold percentage of common stock price trigger	130.00%
Principal amount on conversion rate	$ 1,000
Trading days during observation period	30 days
Conversion observation period	25 days
Conversion ratio	0.00131711
Conversion price (in USD per share) | $ / shares	$ 75.92
Shares issued to settle notes at initial conversion rate (in shares) | shares		5.0
Conversion premium	42.50%
Market price of common stock (in USD per share) | $ / shares	$ 53.28
Redemption rate	100.00%
Carrying amount of the liability component upon issuance	$ 368,300,000
Assumed borrowing rate	7.50%
Carrying amount of the equity component upon issuance	$ 149,200,000
Term	7 years
Remaining discount amortization period				3 years 4 months 24 days
Transaction cost related to issuance of convertible senior note	$ 14,700,000
Events of default percentage of principal and accrued and unpaid interest due and payable upon default	100.00%
Aggregate principal amount repurchased			$ 136,200,000
Aggregate repurchase price paid in cash			186,900,000
Fair value of the liability component immediately before extinguishment			130,700,000
Equity component of repurchased convertible senior notes			56,300,000
Carrying amount of the liability component at settlement			112,400,000
Loss on extinguishment of convertible senior notes			$ 18,400,000
Fair value		$ 514,300,000		$ 514,300,000	$ 596,800,000
2.25% Convertible senior notes due 2024 | Conversion Period One
Debt Instrument [Line Items]
Threshold common stock trading days | d	20
Threshold consecutive common stock trading days | d	30
Threshold percentage of common stock price trigger	130.00%
2.25% Convertible senior notes due 2024 | Conversion Period Two
Debt Instrument [Line Items]
Threshold common stock trading days | d	5
Threshold consecutive common stock trading days | d	5
Principal amount on conversion rate	$ 1,000
Minimum percentage of common stock price trigger	98.00%
2.25% Convertible senior notes due 2024 | Discount rate
Debt Instrument [Line Items]
Discount rate			0.0337

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