Significant Accounting Policies - Revenue Recognition/Income Taxes (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income taxes
Federal, state and local tax provision	$ 0	$ 0	$ 1,500,000	$ 2,000,000