Marketable Securities - Schedule of Maturities (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Debt Securities, Available-for-sale [Line Items]
Fair Value	$ 90,590
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Less than 1 Year	1,511
1-5 Years	4,828
5-10 Years	0
Greater than 10 Years	0
Fair Value	6,339
Government securities - U.S.
Debt Securities, Available-for-sale [Line Items]
Less than 1 Year	771
1-5 Years	11,145
5-10 Years	281
Greater than 10 Years	504
Fair Value	12,701
Other fixed-income securities
Debt Securities, Available-for-sale [Line Items]
Less than 1 Year	0
1-5 Years	9,409
5-10 Years	0
Greater than 10 Years	0
Fair Value	9,409
Debt Securities
Debt Securities, Available-for-sale [Line Items]
Less than 1 Year	2,282
1-5 Years	25,382
5-10 Years	281
Greater than 10 Years	504
Fair Value	$ 28,449

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