Debt - 1.50% Convertible Debentures due 2035 (Details) shares in Millions				1 Months Ended	3 Months Ended
	Nov. 05, 2021 USD ($) shares	Nov. 04, 2021 USD ($)	Sep. 29, 2021	Jun. 30, 2015 USD ($) day	Dec. 31, 2021 USD ($) day shares	Sep. 30, 2021 USD ($) shares	Jun. 30, 2021 USD ($) shares	Dec. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2015 USD ($)	Oct. 24, 2011
Debt Instrument [Line Items]
Face value					$ 889,400,000	$ 918,000,000
Repayments of convertible debt					$ 28,646,000			$ 0
Trading days | day					20
Loss on extinguishment of debt					$ 215,000			$ 0
Aggregate principal amount					889,392,000
Convertible Debentures 1.5% Due 2035
Debt Instrument [Line Items]
Stated percentage				1.50%
Face value				$ 263,900,000
Repayments of convertible debt		$ 100,000
Debt proceeds				$ 253,200,000
Debt issuance, percentage of principal				97.09%
Debt discount				$ 7,700,000
Trading days | day				10
Contingent interest amount per principal				$ 1,200
Accrued interest rate				0.50%
Repurchased face amount		25,000,000							$ 36,500,000
Repurchase amount		$ 100,000							41,300,000
Debt repurchase allocation, debt portion									34,700,000
Debt repurchase allocation - Equity portion									6,600,000
Unamortized discount write-off									2,500,000
Unamortized costs									100,000
Loss on repurchases									$ 800,000
Value of common stock consideration					41,900,000
Redemption price percentage			100.00%
Aggregate principal amount					0
Convertible Debentures 1.5% Due 2035 | Debt Instrument, Redemption, Period One
Debt Instrument [Line Items]
Repayments of convertible debt	$ 25,100,000				25,100,000	137,400,000
Repurchased face amount					$ 25,100,000	137,400,000
Debt repurchase allocation, debt portion						136,000,000
Debt repurchase allocation - Equity portion						225,100,000
Unamortized discount write-off						2,400,000
Unamortized costs						100,000
Loss on repurchases						$ 1,100,000
Shares converted (in shares) | shares	0.8				0.8	4.1
Value of common stock consideration						$ 223,700,000
Aggregate principal amount					$ 0
Convertible Debentures 1.5% Due 2035 | Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Repayments of convertible debt							$ 500,000
Repurchased face amount							64,900,000
Debt repurchase allocation, debt portion							64,200,000
Debt repurchase allocation - Equity portion							102,500,000
Unamortized discount write-off							$ 1,400,000
Shares converted (in shares) | shares							3.2
Loss on extinguishment of debt							$ 1,100,000
Inducement expense							400,000
Interest expense earned							100,000
Stock issued							$ 166,700,000
Convertible Debentures 1.5% Due 2035 | Minimum
Debt Instrument [Line Items]
Percentage of stock closing price to debt conversion price				130.00%
Number of trading days				20 days
Senior Convertible Debentures due in 2031
Debt Instrument [Line Items]
Stated percentage											2.75%
Repayments of convertible debt				$ 256,200,000
Repurchased face amount										$ 38,300,000
Ending on Last Trading Day of Previous Fiscal Quarter | Convertible Debentures 1.5% Due 2035
Debt Instrument [Line Items]
Number of consecutive trading days				30 days