Equity Compensation Plans - Stock Incentive Plan (Details Textual) - Stock Incentive Plan 2005	1 Months Ended	12 Months Ended
	May 31, 2020 shares	Dec. 31, 2020 shares	Apr. 30, 2018 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares approved for issuance under incentive plan	3,600,000
Number of shares approved for issuance under incentive plan	25,000,000.0		21,400,000
Number of shares counted for every share granted		2
Stockholder approved shares available for issuance		5,800,000
Stockholder approved shares available for grant		5,500,000