XML 42 R31.htm IDEA: XBRL DOCUMENT v3.20.2
Marketable Securities - Available-for-sale Securities by Major Security Type (Details) - USD ($)
$ in Thousands
Sep. 30, 2020
Dec. 31, 2019
Marketable Securities [Line Items]    
Amortized cost $ 2,980 $ 4,521
Gross unrealized holding gains 38 26
Gross unrealized holding losses (5) (4)
Estimated fair value 3,013 4,543
Corporate bonds and notes [Member]    
Marketable Securities [Line Items]    
Amortized cost 1,714 1,814
Gross unrealized holding gains 32 21
Gross unrealized holding losses (5) (3)
Estimated fair value 1,741 1,832
Municipal bonds [Member]    
Marketable Securities [Line Items]    
Amortized cost 1,266 2,707
Gross unrealized holding gains 6 5
Gross unrealized holding losses (1)
Estimated fair value $ 1,272 $ 2,711