Fair Value Measurements - Assets Measured at Fair Value on Recurring Basis (Details) - Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Equity Security [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	$ 10	$ 10
Equity Mutual Fund [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	5,296	5,621
U.S. Treasury Mutual Fund [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	12,513	8,915
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Security [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	10	10
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Mutual Fund [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Treasury Mutual Fund [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	12,513	8,915
Significant Other Observable Inputs (Level 2) [Member] | Equity Security [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Equity Mutual Fund [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	5,296	5,621
Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury Mutual Fund [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Security [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Mutual Fund [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | U.S. Treasury Mutual Fund [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	$ 0	$ 0