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Stock incentive plans, Stock incentive plans (Details)
12 Months Ended
Dec. 31, 2019
Plan
shares
Stock incentive plans [Abstract]  
Number of primary stock incentive plans | Plan 2
Stock Options [Member]  
Stock incentive plans [Abstract]  
Exercise prices of options granted equals percentage of fair market value of common stock 100.00%
Term of award 10 years
Stock Options [Member] | Minimum [Member]  
Stock incentive plans [Abstract]  
Vesting period 2 years
Stock Options [Member] | Maximum [Member]  
Stock incentive plans [Abstract]  
Vesting period 5 years
2014 Equity Incentive Plan [Member]  
Stock incentive plans [Abstract]  
Number of shares authorized (in shares) 1,400,000
Number of shares available for grant (in shares) 332,541
2014 Equity Incentive Plan [Member] | Stock Options [Member]  
Stock incentive plans [Abstract]  
Term of award 10 years