Conversion Features (Details) $ in Millions	9 Months Ended	12 Months Ended
Dec. 31, 2017	Mar. 31, 2018 USD ($) day
2015 Senior Subordinated Convertible Debt
Debt Instrument [Line Items]
Threshold percentage of stock price trigger	130.00%
If-converted value in excess of principal \| $		$ 1,141.7
Convertible Debt
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	100.00%
Convertible Debt \| Debt Instrument, Redemption, Period One
Debt Instrument [Line Items]
Threshold percentage of stock price trigger		130.00%
Threshold trading days		20
Threshold consecutive trading days		30
Convertible Debt \| Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Threshold percentage of stock price trigger		98.00%
Threshold trading days		5
Threshold consecutive trading days		10

The amount by which the convertible debt's if-converted value exceeds its principle amount at the balance sheet date, regardless of whether the instrument is currently convertible. This element applies to public companies only.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6928298&loc=SL6031898-161870

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- Definition

Threshold period of specified consecutive trading days within which common stock price to conversion price of convertible debt instrument must exceed threshold percentage for specified number of trading days to trigger conversion feature.

+ References

No definition available.

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- Definition

Minimum percentage of common stock price to conversion price of convertible debt instruments to determine eligibility of conversion.

+ References

No definition available.

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- Definition

Threshold number of specified trading days that common stock price to conversion price of convertible debt instruments must exceed threshold percentage within a specified consecutive trading period to trigger conversion feature.

+ References

No definition available.

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- Definition

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.

+ References

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

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