Debt and Capital Leases - Issuance of Convertible Senior Notes (Details)	3 Months Ended
Jun. 30, 2018 USD ($) $ / shares
Debt Instrument [Line Items]
Debt issuance transaction costs	$ 12,000,000
Convertible Senior Notes, due 2048 \| Convertible Debt
Debt Instrument [Line Items]
Aggregate principal amount	$ 575,000,000
Interest rate, stated percentage	2.75%
Conversion price per common share (in usd per share) \| $ / shares	$ 47.74
Conversion ratio	20.9479
Debt, estimated fair value	$ 472,000,000
Carrying amount of equity component	$ 103,000,000
Debt discount amortization period	7 years
Debt deferred financing costs amortization period	7 years
Convertible Senior Notes, due 2048 \| Convertible Debt \| Deferred Financing Costs
Debt Instrument [Line Items]
Debt issuance transaction costs	$ 10,000,000
Convertible Senior Notes, due 2048 \| Convertible Debt \| Additional Paid-in Capita
Debt Instrument [Line Items]
Debt issuance transaction costs	$ 2,000,000

Amortization Period, Debt Issuance Costs

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- Definition

The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

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

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

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Remaining amortization period for discount on the liability component of convertible debt which may be settled in cash upon conversion, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Face (par) amount of debt instrument at time of issuance.

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

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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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Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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