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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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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No definition available.

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Fair value amount of debt instrument that was repurchased.

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No definition available.

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Gross amount of debt extinguished.

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No definition available.

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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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Decrease in noncontrolling interest (for example, but not limited to, redeeming or purchasing the interests of noncontrolling shareholders, issuance of shares (interests) by the non-wholly owned subsidiary to the parent entity for other than cash, and a buyback of shares (interest) by the non-wholly owned subsidiary from the noncontrolling interests).

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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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Price of a single share of a number of saleable stocks of a company.

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No definition available.

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Debt - Encore Convertible Notes (Narrative) (Details)					1 Months Ended	9 Months Ended
Debt - Encore Convertible Notes (Narrative) (Details)	Feb. 27, 2017 $ / shares	Mar. 05, 2014 $ / shares	Jun. 24, 2013 $ / shares	Nov. 27, 2012 $ / shares	Mar. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Mar. 31, 2014 USD ($)	Jul. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Debt Instrument [Line Items]
Proceeds from issuance of convertible senior notes						$ 150,000,000	$ 0
Repayment of convertible senior notes						$ 60,406,000	$ 0
2017 Convertible Senior Notes
Debt Instrument [Line Items]
Debt instrument, stated interest rate						3.00%
Initial conversion price (in dollars per share) \| $ / shares				$ 31.56
Closing stock price at date of issuance (in dollars per share) \| $ / shares				$ 25.66
Conversion rate (shares per $1,000 principal amount)				0.0316832
2020 Convertible Notes
Debt Instrument [Line Items]
Debt instrument, stated interest rate						3.00%
Initial conversion price (in dollars per share) \| $ / shares			$ 45.72
Closing stock price at date of issuance (in dollars per share) \| $ / shares			$ 33.35
Conversion rate (shares per $1,000 principal amount)			0.0218718
2021 Convertible Notes
Debt Instrument [Line Items]
Debt instrument, stated interest rate						2.875%
Initial conversion price (in dollars per share) \| $ / shares		$ 59.39
Closing stock price at date of issuance (in dollars per share) \| $ / shares		$ 47.51
Conversion rate (shares per $1,000 principal amount)		0.0168386
2022 Convertible Notes
Debt Instrument [Line Items]
Debt instrument, stated interest rate						3.25%
Initial conversion price (in dollars per share) \| $ / shares	$ 45.57
Closing stock price at date of issuance (in dollars per share) \| $ / shares	$ 35.05
Conversion rate (shares per $1,000 principal amount)	0.0219467
Convertible notes \| 2017 Convertible Senior Notes
Debt Instrument [Line Items]
Debt issued					$ 50,000,000.0					$ 115,000,000.0
Debt instrument, stated interest rate										3.00%
Repayment of convertible senior notes					60,400,000
Consideration allocated to extinguishment of liability					49,700,000
Consideration allocated to re-acquisition of equity component					10,700,000
Carrying value of repurchased portion of debt					48,900,000.0
Loss recognized on repurchase transaction					800,000
Convertible notes \| 2020 Convertible Notes
Debt Instrument [Line Items]
Debt issued									$ 172,500,000.0
Debt instrument, stated interest rate									3.00%
Convertible notes \| 2021 Convertible Notes
Debt Instrument [Line Items]
Debt issued								$ 161,000,000.0
Debt instrument, stated interest rate								2.875%
Convertible notes \| 2022 Convertible Notes
Debt Instrument [Line Items]
Debt issued					$ 150,000,000.0
Debt instrument, stated interest rate					3.25%
Proceeds from issuance of convertible senior notes					$ 145,300,000