Debt (Tables)

9 Months Ended

Sep. 30, 2021

Debt Disclosure [Abstract]

Schedule of Net Carrying Amount of Liability and Equity Components of Notes

The net carrying amount of the liability and equity components of the 2026 Notes and 2024 Notes as of September 30, 2021 were as follows (in millions):

	2024 Notes			2026 Notes			Total
Liability component:
Principal	$	690.0		$	874.5		$	1,564.5
Unamortized debt discount		(66.4	)		(147.0	)		(213.4	)
Unamortized transaction costs		(8.3	)		(12.6	)		(20.9	)
Net carrying amount	$	615.3		$	714.9		$	1,330.2
Equity component, net of transaction costs	$	114.9		$	163.7		$	278.6

The net carrying amount of the liability and equity components of the 2026 Notes and 2024 Notes as of December 31, 2020 were as follows (in millions):

	2024 Notes			2026 Notes			Total
Liability component:
Principal	$	690.0		$	874.5		$	1,564.5
Unamortized debt discount		(83.8	)		(166.1	)		(249.9	)
Unamortized transaction costs		(10.5	)		(14.2	)		(24.7	)
Net carrying amount	$	595.7		$	694.2		$	1,289.9
Equity component, net of transaction costs	$	114.9		$	163.7		$	278.6

Schedule of Interest Expense Recognized Related to Notes

Interest expense recognized related to the Notes was as follows (in millions):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
Contractual interest expense	$	0.4	$	0.4	$	1.3	$	1.3
Amortization of debt discount		12.3		5.6		36.4		16.7
Amortization of transaction costs		1.2		0.7		3.8		2.1
Total	$	13.9	$	6.7	$	41.5	$	20.1