Long-Term Debt - Summary of Convertible Subordinated Notes (Details) shares in Millions, $ in Millions	1 Months Ended	12 Months Ended
Jan. 31, 2017 shares	Dec. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Convertible subordinated notes		$ 35.6	$ 0.0
Convertible subordinated notes		35.6	0.0
4 1/16% Debentures
Debt Instrument [Line Items]
Convertible subordinated notes		$ 35.6	$ 0.0
Debt instrument interest rate stated percentage			4.0625%
Redemption price rate on principal amount		100.00%
Convertible subordinated notes		$ 35.6
Convertible debentures into shares of common stock (in shares) \| shares	3.9

Including the current and noncurrent portions, carrying value as of the balance sheet date of a written promise to pay a note, initially due after one year or beyond the operating cycle if longer, which can be exchanged for a specified amount of one or more securities (typically common stock), at the option of the issuer or the holder.

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-Publisher FASB
-Name Accounting Standards Codification
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Including the current and noncurrent portions, the carrying value of convertible subordinated debt, as of the balance sheet date, initially scheduled to be repaid after one year or beyond the normal operating cycle if longer. This form of debt 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, and places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

+ References

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The number of equity instruments that the holder of the debt instrument would receive if the debt was converted to equity.

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

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Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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