Debt Instruments - Convertible Debt Offering Due 2020 (Details) |
9 Months Ended | ||||
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May 24, 2018
USD ($)
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Dec. 09, 2015
USD ($)
$ / shares
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Sep. 30, 2018
USD ($)
$ / shares
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Sep. 30, 2017
USD ($)
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Dec. 31, 2017
USD ($)
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| Debt Instruments | |||||
| Carrying value | $ 255,272,000 | $ 273,014,000 | |||
| Loss on extinguishment of convertible debt | $ (14,600,000) | $ 0 | |||
| Convertible debt | Convertible senior notes due 2020 | |||||
| Debt Instruments | |||||
| Aggregate principal amount | $ 157,400,000 | $ 345,000,000.0 | |||
| Interest rate | 1.75% | 1.75% | |||
| Net proceeds from sale of debt | $ 336,500,000 | ||||
| Payments for capped call transactions | $ 43,200,000 | ||||
| Carrying value | 192,900,000 | $ 127,647,000 | $ 273,014,000 | ||
| Loss on extinguishment of convertible debt | $ 14,600,000 | ||||
| Debt instrument, conversion ratio | 0.060905 | ||||
| Debt instrument, conversion price (in dollars per share) | $ / shares | $ 16.42 | $ 16.42 | |||
| Value of debt | $ 233,500,000 | $ 148,700,000 | |||
| Carrying amount of equity component reported in additional paid-in-capital | 103,000,000.0 | ||||
| Debt fees and expenses | $ 2,600,000 | ||||
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- Definition The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The price per share of the conversion feature embedded in the debt instrument. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Face (par) amount of debt instrument at time of issuance. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of the fee that accompanies borrowing money under the debt instrument. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Contractual interest rate for funds borrowed, under the debt agreement. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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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. No definition available.
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- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition The cash outflow for derivative instruments during the period, which are classified as financing activities, excluding those designated as hedging instruments. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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