Stock-based Payments and Director Fees - Grants of Restricted Stock Units to Directors and Employees (Details) - Long Term Incentive Plan - Restricted stock - $ / shares	3 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Employee And Service Provider
Shares
Shares, nonvested (in shares)	236,310	163,083	163,083	170,750	114,334	114,334	163,083	114,334
Shares vested (in shares)	(65,305)	0	0	(50,334)	0	0
Shares forfeited (in shares)	(14,168)	0	0	(2,000)	0	0
Shares granted (in shares)	152,700	0	0	108,750	0	0
Weighted Average Grant Date Fair Value
Per share grant fair value (in dollars per share)	$ 12.01	$ 11.07	$ 11.07	$ 11.11	$ 13.83	$ 13.83	$ 11.07	$ 13.83
Shares vested (in dollars per share)	11.74	0	0	13.86	0	0
Shares forfeited (in dollars per share)	10.88	0	0	12.06	0	0
Shares granted (in dollars per share)	$ 12.79	$ 0	$ 0	$ 9.55	$ 0	$ 0
Director
Shares
Shares, nonvested (in shares)	8,000	8,000	0	0	0	0	0	0
Shares vested (in shares)	0	(8,000)	(2,000)	0	0	0
Shares forfeited (in shares)	0	0	0	0	0	0
Shares granted (in shares)	0	16,000	2,000	0	0	0
Weighted Average Grant Date Fair Value
Per share grant fair value (in dollars per share)	$ 12.60	$ 12.60	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Shares vested (in dollars per share)	0	12.60	12.00	0	0	0
Shares forfeited (in dollars per share)	0	0	0	0	0	0
Shares granted (in dollars per share)	$ 0	$ 12.60	$ 12.00	$ 0	$ 0	$ 0