Investments - Schedule of Proceeds From Sales and Maturities of Marketable Securities Plus the Resulting Realized Gains and Losses (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Investments Debt And Equity Securities [Abstract]
Proceeds from the sales and maturities of marketable securities	$ 55,978	$ 79,500
Realized gains		1
Realized losses	$ 492	$ 4

The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities (held-to-maturity or available-for-sale) during the period.

No definition available.

Name:	us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration