| Marketable Securities  - Continuous Unrealized Loss Position (Details) $ in Thousands | Mar. 31, 2020  USD ($) | 
|---|---|
| Debt Securities, Available-for-sale [Line Items] | |
| Fair Value | $ 320,429 | 
| Gross Unrealized Losses | (3,319) | 
| Corporate debt securities | |
| Debt Securities, Available-for-sale [Line Items] | |
| Fair Value | 304,859 | 
| Gross Unrealized Losses | (3,301) | 
| Municipal securities | |
| Debt Securities, Available-for-sale [Line Items] | |
| Fair Value | 2,891 | 
| Gross Unrealized Losses | (9) | 
| U.S. Government agency securities | |
| Debt Securities, Available-for-sale [Line Items] | |
| Fair Value | 10,669 | 
| Gross Unrealized Losses | (8) | 
| U.S. Treasury securities | |
| Debt Securities, Available-for-sale [Line Items] | |
| Fair Value | 2,010 | 
| Gross Unrealized Losses | $ (1) | 
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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position without allowance for credit loss. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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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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