XML 72 R59.htm IDEA: XBRL DOCUMENT v3.10.0.1
Fair value of financial instruments and investments - Marketable Securities, Balance Sheet Disclosures (Details) - USD ($)
$ in Thousands
Dec. 31, 2018
Dec. 31, 2017
Marketable securities on the balance sheet    
Less Than 12 Months $ 58,088 $ 69,377
More Than 12 Months 0 10,077
Commercial paper    
Marketable securities on the balance sheet    
Less Than 12 Months 31,699 13,827
More Than 12 Months 0 0
Corporate debt securities    
Marketable securities on the balance sheet    
Less Than 12 Months 26,389 55,550
More Than 12 Months $ 0 $ 10,077