Fair Value Measurements (Fair Value Measurements On A Recurring Basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, Carrying amount	$ 2,262	$ 8,785	$ 1,025	$ 1,057
Equity Securities, Fair Value	6,790	45
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, Carrying amount	765	797
Cash equivalents, Fair Value	765	797
Commercial Paper [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, Fair Value	765	797
Commercial Paper [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, Fair Value	0	0
Commercial Paper [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, Fair Value	0	0
Treasury Bills [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, Carrying amount	1,000	7,734
Cash equivalents, Fair Value	1,000	7,734
Treasury bills, Carrying amount	6,748
Treasury bills, Fair Value	6,748
Treasury Bills [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, Fair Value	1,000	7,734
Treasury bills, Fair Value	6,748
Treasury Bills [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, Fair Value	0	0
Treasury bills, Fair Value	0
Treasury Bills [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, Fair Value	0	0
Treasury bills, Fair Value	0
Limited Marketable Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, Carrying amount	42	45
Equity Securities, Fair Value	42	45
Limited Marketable Company [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, Fair Value	0	0
Limited Marketable Company [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, Fair Value	0	0
Limited Marketable Company [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, Fair Value	$ 42	$ 45