| Convertible Senior Notes (Details) $ in Thousands | 3 Months Ended | 12 Months Ended | |
|---|---|---|---|
| Mar. 31, 2020  USD ($) | Dec. 31, 2019  USD ($) | Dec. 31, 2017  USD ($) | |
| Debt Instrument, Redemption [Line Items] | |||
| Proceeds from convertible senior notes | $ 282,200 | ||
| Convertible senior notes conversion ratio | 0.0631793 | 0.0631793 | |
| Convertible senior notes | $ 285,238 | $ 284,954 | |
| Convertible Debt [Member] | |||
| Debt Instrument, Redemption [Line Items] | |||
| Aggregate principal amount | $ 287,500 | ||
| Convertible senior notes interest rate per annum | 6.25% | ||
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- Definition Including the current and noncurrent portions, carrying value as of the balance sheet date of a written promise to pay a note, initially due after one year or beyond the operating cycle if longer, which can be exchanged for a specified amount of one or more securities (typically common stock), at the option of the issuer or the holder. 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 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 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 The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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