Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($)	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Sep. 30, 2017	1,805,053	(424,307)
Balance at Sep. 30, 2017	$ 18,000	$ (4,000)	$ 1,755,000	$ 57,150,000	$ 100,822,000	$ 159,741,000
Net (loss) income				14,739,000		14,739,000
Net decrease in unrealized appreciation of marketable securities (net of taxes)					12,118,000	12,118,000
Balance at Dec. 31, 2017	$ 18,000	$ (4,000)	1,755,000	71,889,000	112,940,000	186,598,000
Balance (in shares) at Dec. 31, 2017	1,805,053	(424,307)
Balance (in shares) at Sep. 30, 2017	1,805,053	(424,307)
Balance at Sep. 30, 2017	$ 18,000	$ (4,000)	1,755,000	57,150,000	100,822,000	159,741,000
Net (loss) income						14,507,000
Net decrease in unrealized appreciation of marketable securities (net of taxes)						(1,743,000)
Balance at Mar. 31, 2018	$ 18,000	$ (4,000)	1,755,000	51,667,000	116,516,000	169,952,000
Balance (in shares) at Mar. 31, 2018	1,805,053	(424,307)
Balance (in shares) at Dec. 31, 2017	1,805,053	(424,307)
Balance at Dec. 31, 2017	$ 18,000	$ (4,000)	1,755,000	71,889,000	112,940,000	186,598,000
Net (loss) income				(232,000)		(232,000)
Net decrease in unrealized appreciation of marketable securities (net of taxes)					(13,861,000)	(13,861,000)
Balance at Mar. 31, 2018	18,000	(4,000)	1,755,000	51,667,000	116,516,000	169,952,000
Stranded tax effects reclassification resulted from Tax Cuts and Jobs Act				(19,990,000)	19,990,000
Realized gains on bond investment, net of taxes					(2,553,000)	(2,553,000)
Balance (in shares) at Mar. 31, 2018	1,805,053	(424,307)
Balance (in shares) at Sep. 30, 2018	1,805,053	(424,307)
Balance at Sep. 30, 2018	$ 18,000	$ (4,000)	1,755,000	45,361,000	115,786,000	162,916,000
Net (loss) income				(21,533,000)		(21,533,000)
Balance at Dec. 31, 2018	18,000	(4,000)	1,755,000	139,614,000		141,383,000
Adoption of new accounting pronouncement at Sep. 30, 2018				115,786,000	(115,786,000)
Balance (in shares) at Dec. 31, 2018	1,805,053	(424,307)
Balance (in shares) at Sep. 30, 2018	1,805,053	(424,307)
Balance at Sep. 30, 2018	$ 18,000	$ (4,000)	1,755,000	45,361,000	115,786,000	162,916,000
Net (loss) income						(16,515,000)
Net decrease in unrealized appreciation of marketable securities (net of taxes)
Balance at Mar. 31, 2019	18,000	(4,000)	1,755,000	144,632,000		146,401,000
Adoption of new accounting pronouncement at Sep. 30, 2018				115,786,000	(115,786,000)
Balance (in shares) at Mar. 31, 2019	1,805,053	(424,307)
Balance (in shares) at Dec. 31, 2018	1,805,053	(424,307)
Balance at Dec. 31, 2018	$ 18,000	$ (4,000)	1,755,000	139,614,000		141,383,000
Net (loss) income				5,018,000		5,018,000
Net decrease in unrealized appreciation of marketable securities (net of taxes)
Balance at Mar. 31, 2019	$ 18,000	$ (4,000)	$ 1,755,000	$ 144,632,000		$ 146,401,000
Balance (in shares) at Mar. 31, 2019	1,805,053	(424,307)