Debt - Junior Convertible Securities (Details) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2022 USD ($) d $ / shares	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)
Debt Instrument [Line Items]
Debt	$ 2,577.9		$ 2,490.4
Junior convertible securities
Debt Instrument [Line Items]
Debt	382.6		295.6
Junior Convertible Trust Preferred Securities \| Junior convertible securities
Debt Instrument [Line Items]
Debt	$ 386.3
Debt interest rate	5.15%
Unamortized debt issuance costs	$ 3.7		$ 3.9
Conversion ratio per share of common stock	0.2558
Face amount of convertible security (in usd per share) \| $ / shares	$ 50.00
Adjusted conversion price (in dollars per share) \| $ / shares	$ 195.47
Convertible debt, threshold trading days \| d	20
Convertible debt, threshold consecutive trading days \| d	30
Debt instrument, convertible, threshold percentage	1.30
Repayments of convertible debt	$ 16.5	$ 15.0
Deferred tax liabilities, net, decrease resulting from repurchase of junior convertible securities	$ 2.7	$ 3.3

Debt Instrument, Convertible, Threshold Percentage

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- Definition

Debt Instrument, Individual Security, Face Amount

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- Definition

Deferred Tax Liabilities, Net, Decrease Resulting From Repurchase Of Debt

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- Definition

The price per share of the conversion feature embedded in the debt instrument.

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- Definition

Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

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- Definition

Threshold period of specified consecutive trading days within which common stock price to conversion price of convertible debt instrument must exceed threshold percentage for specified number of trading days to trigger conversion feature.

+ References

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Threshold number of specified trading days that common stock price to conversion price of convertible debt instruments must exceed threshold percentage within a specified consecutive trading period to trigger conversion feature.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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- Definition

The cash outflow from the repayment of a long-term debt instrument which can be exchanged for a specified amount of another security, typically the entity's common stock, at the option of the issuer or the holder.

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- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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