Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Schedule of Financial Instruments Measured at Fair Value on Recurring Basis (Details)

v3.19.3
Fair Value Measurements - Schedule of Financial Instruments Measured at Fair Value on Recurring Basis (Details) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Summary of financial instruments measured at fair value on a recurring basis          
Common shares of CO2 Solutions         $ 588,000
Total         31,813,000
Other Expense [Member]          
Summary of financial instruments measured at fair value on a recurring basis          
Gain (loss) on equity securities   $ (25,000)   $ (20,000)  
Common Shares of Co Two Solution [Member] | Other Expense [Member]          
Summary of financial instruments measured at fair value on a recurring basis          
Gain (loss) on equity securities $ (400,000)   $ (500,000)    
Available-for-sale Securities [Member]          
Summary of financial instruments measured at fair value on a recurring basis          
Common shares of CO2 Solutions         $ 588,000
Investment owned, balance (in shares)         10,000,000
Available-for-sale Securities [Member] | Common Shares of Co Two Solution [Member]          
Summary of financial instruments measured at fair value on a recurring basis          
Common shares of CO2 Solutions 0   0    
Money Market Funds [Member]          
Summary of financial instruments measured at fair value on a recurring basis          
Money market funds 73,450,000   73,450,000   $ 31,225,000
Fair Value, Inputs, Level 1 [Member]          
Summary of financial instruments measured at fair value on a recurring basis          
Total         31,856,000
Fair Value, Inputs, Level 1 [Member] | Available-for-sale Securities [Member]          
Summary of financial instruments measured at fair value on a recurring basis          
Common shares of CO2 Solutions         588,000
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]          
Summary of financial instruments measured at fair value on a recurring basis          
Money market funds $ 73,450,000   $ 73,450,000   $ 31,225,000