Debt and Credit Facilities 1.5% Convertible Debentures due 2035 (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Jun. 01, 2015
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 2,437,000	$ 2,437,000
Debt Issuance Costs, Noncurrent, Net	$ 760	$ 843
Convertible Debentures One Point Five Percent Due November One Twenty Thirty Five [Member] [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 263,900
Debt Instrument, Interest Rate, Stated Percentage	1.50%	1.50%
Debt Instrument, Convertible, Conversion Price			$ 23.26
Debt issuance Percentage of Principal Amount			97.09%
Debt Instrument, Unamortized Discount (Premium), Net			$ 7,700
Debt Instrument, Unamortized Discount	$ 30,358	$ 32,845
Convertible Debt, Noncurrent			208,600
Debt Instrument, Convertible, Carrying Amount of Equity Component			$ 55,300

Debt issuance Percentage of Principal Amount

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- Definition

Carrying amount of long-term convertible debt as of the balance sheet date, net of the amount due in the next twelve months or greater than the normal operating cycle, if longer. The debt is convertible into another form of financial instrument, typically the entity's common stock.

+ References

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-Paragraph 1
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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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- Definition

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

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- Definition

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

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- Definition

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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No definition available.

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- Definition

Amount, after accumulated amortization, of debt discount.

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Amount, after accumulated amortization, of debt discount (premium).

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- Definition

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

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