Selected Quarterly Financial Data (unaudited) (Schedule of Selected Quarterly Financial Data (unaudited)) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 9,240,000	$ 7,984,000	$ 8,503,000	$ 8,278,000	$ 8,913,000	$ 8,495,000	$ 10,844,000	$ 10,935,000	$ 34,005,000	$ 39,187,000	$ 45,890,000
Net (loss) income	(1,634,000)	89,309,000	(42,587,000)	(1,057,000)	(16,750,000)	(80,516,000)	51,055,000	1,112,000	44,031,000	(45,099,000)	(1,072,000)
Net (loss) income attributable to common shareholders	$ (4,322,000)	$ 86,621,000	$ (45,275,000)	$ (3,745,000)	$ (19,438,000)	$ (83,204,000)	$ 48,367,000	$ (1,576,000)	$ 33,279,000	$ (55,851,000)	$ (11,824,000)
Per common share (basic) - continuing operations	$ (0.28)	$ (2.87)	$ (2.78)	$ (0.71)	$ (1.07)	$ (4.97)	$ 3.11	$ (0.60)	$ (6.64)	$ (3.53)	$ (2.59)
Per common share (diluted) - continuing operations	(0.28)	(2.87)	(2.78)	(0.71)	(1.07)	(4.97)	3.11	(0.60)	(6.64)	(3.53)	(2.59)
Per common share (basic) - discontinued operations	0.03	9.29	(0.63)	0.43	(0.30)	(1.31)	0.41	0.49	9.12	(0.71)	1.67
Per common share (diluted) - discontinued operations	0.03	9.29	(0.63)	0.43	(0.30)	(1.31)	0.41	0.49	9.12	(0.71)	1.67
Net (loss) income per common share attributable to common shareholders, basic	(0.25)	6.42	(3.41)	(0.28)	(1.37)	(6.28)	3.52	(0.11)	2.48	(4.24)	(0.92)
Net (loss) income per common share attributable to common shareholders, diluted	$ (0.25)	$ 6.42	$ (3.41)	$ (0.28)	$ (1.37)	$ (6.28)	$ 3.52	$ (0.11)	$ 2.48	$ (4.24)	$ (0.92)