Aggregate Principal Amount of Senior Notes, Redemption Price, Percentage

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Debt Instrument Conversion Circumstance, Number of Consecutive Business Days

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Debt Instrument Conversion Circumstance, Number of Consecutive Trading Days

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Debt Instrument Conversion Circumstance, Number of Trading Days

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Principal Amount Per Note Used in Conversion Rate

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Ratio of Common Stock Closing Price to Debt Conversion Price, Percentage

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- Definition

Adjustment to additional paid in capital resulting from the recognition of convertible debt instruments as two separate components - a debt component and an equity component. This bifurcation may result in a basis difference associated with the liability component that represents a temporary difference for purposes of applying accounting for income taxes. The initial recognition of deferred taxes for the tax effect of that temporary difference is as an adjustment to additional paid in capital.

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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.

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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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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, after accumulated amortization, of debt discount.

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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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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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The cash inflow from the issuance 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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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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Credit Facilities and Debt - 2.75% Convertible Notes due 2031 (Details) - USD ($)	3 Months Ended			12 Months Ended
	Sep. 30, 2019	Dec. 31, 2017	Dec. 31, 2014	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2012	Nov. 01, 2017	Jun. 30, 2017	Dec. 07, 2015	Jun. 01, 2015	Oct. 24, 2011
Debt Instrument [Line Items]
Long-term debt, face value	$ 2,137,000,000.0			$ 2,137,000,000.0	$ 2,437,000,000.0
Loss on extinguishment of debt				910,000	(348,000)	$ 18,565,000
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt						96,160,000
Debt Issuance Costs, Noncurrent, Net	511,000			511,000	843,000
2.75% Convertible Debentures due November 1, 2031
Debt Instrument [Line Items]
Long-term debt, face value								$ 46,600,000		$ 395,500,000		$ 690,000,000.0
Loss on extinguishment of debt						(17,700,000)
Repayments of Convertible Debt	256,200,000	$ 331,200,000	$ 38,300,000	$ 17,800,000	$ 38,300,000	$ 256,200,000
Aggregate Principal Amount of Senior Notes, Redemption Price, Percentage				100.00%
Debt Instrument, Convertible, Conversion Price												$ 32.30
Principal Amount Per Note Used In Conversion Rate	$ 1,000			$ 1,000
Debt Instrument Conversion Circumstance Number Of Consecutive Business Days				5 days
Convertible debentures, interest rate	2.75%		2.75%	2.75%	2.75%							2.75%
Convertible Debt, Noncurrent												$ 533,600,000
Debt Instrument, Convertible, Carrying Amount of Equity Component												$ 156,400,000
Proceeds from Convertible Debt							$ 676,100,000
Debt Instrument, Unamortized Discount	$ 0			$ 0	$ 0
Convertible Debentures One Percent Due Twenty Thirty Five [Member]
Debt Instrument [Line Items]
Long-term debt, face value										$ 676,500,000
Loss on extinguishment of debt					$ (2,400,000)
Debt Instrument, Convertible, Conversion Price										$ 27.22
Convertible debentures, interest rate					1.00%				1.00%
Convertible Debt, Noncurrent										$ 495,400,000
Debt Instrument, Convertible, Carrying Amount of Equity Component										$ 181,100,000
Debt Instrument, Unamortized Discount	$ (91,600,000)			$ (91,600,000)	$ (116,900,000)
Convertible Debentures One Point Five Percent Due November One Twenty Thirty Five [Member] [Member]
Debt Instrument [Line Items]
Long-term debt, face value											$ 263,900,000
Aggregate Principal Amount of Senior Notes, Redemption Price, Percentage				100.00%
Debt Instrument, Convertible, Conversion Price											$ 23.26
Debt Instrument Conversion Circumstance Number Of Consecutive Business Days				5 days
Convertible debentures, interest rate	1.50%			1.50%	1.50%
Convertible Debt, Noncurrent											$ 208,600,000
Debt Instrument, Convertible, Carrying Amount of Equity Component											$ 55,300,000
Debt Instrument, Unamortized Discount	$ (22,700,000)			$ (22,700,000)	$ (32,800,000)
Minimum \| 2.75% Convertible Debentures due November 1, 2031
Debt Instrument [Line Items]
Ratio of Common Stock Closing Price to Debt Conversion Price, Percentage	130.00%			130.00%
Debt Instrument Conversion Circumstance Number Of Trading Days				20 days
Minimum \| Convertible Debentures One Percent Due Twenty Thirty Five [Member]
Debt Instrument [Line Items]
Ratio of Common Stock Closing Price to Debt Conversion Price, Percentage										130.00%
Debt Instrument Conversion Circumstance Number Of Trading Days					20 days
Minimum \| Convertible Debentures One Point Five Percent Due November One Twenty Thirty Five [Member] [Member]
Debt Instrument [Line Items]
Ratio of Common Stock Closing Price to Debt Conversion Price, Percentage	130.00%			130.00%
Debt Instrument Conversion Circumstance Number Of Trading Days				20 days
Maximum \| 2.75% Convertible Debentures due November 1, 2031
Debt Instrument [Line Items]
Ratio of Common Stock Closing Price to Debt Conversion Price, Percentage	98.00%			98.00%
Maximum \| Convertible Debentures One Percent Due Twenty Thirty Five [Member]
Debt Instrument [Line Items]
Ratio of Common Stock Closing Price to Debt Conversion Price, Percentage										98.00%
Debt Instrument Conversion Circumstance Number Of Trading Days					30 days
Principal Amount Per Note Used In Conversion Rate										$ 1,000
Maximum \| Convertible Debentures One Point Five Percent Due November One Twenty Thirty Five [Member] [Member]
Debt Instrument [Line Items]
Ratio of Common Stock Closing Price to Debt Conversion Price, Percentage	98.00%			98.00%
Ending on Last Trading Day of Previous Fiscal Quarter [Member] \| 2.75% Convertible Debentures due November 1, 2031
Debt Instrument [Line Items]
Debt Instrument Conversion Circumstance Number Of Consecutive Trading Days				30 days
Ending on Last Trading Day of Previous Fiscal Quarter [Member] \| Convertible Debentures One Point Five Percent Due November One Twenty Thirty Five [Member] [Member]
Debt Instrument [Line Items]
Debt Instrument Conversion Circumstance Number Of Consecutive Trading Days				30 days