Condensed Statements Of Cash Flows (USD $)	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Cash flows from operating activities:
Cash received from royalties and rents	$ 4,363,142		$ 8,203,545
Cash paid to suppliers and employees	(712,325)		(720,172)
Interest received	28,176		5,014
NET CASH PROVIDED BY OPERATING ACTIVITIES	3,678,993		7,488,387
Cash flows from investing activities:
United States Treasury securities purchased	(675,000)		(1,625,000)
United States Treasury securities matured	5,225,000		2,600,000
NET CASH PROVIDED BY INVESTING ACTIVITIES	4,550,000		975,000
Cash flows from financing activities:
Distributions paid	(7,875,000)		(8,625,000)
NET CASH USED IN FINANCING ACTIVITIES	(7,875,000)		(8,625,000)
Net increase (decrease) in cash and cash equivalents	353,993		(161,613)
Cash and cash equivalents at beginning of year	643,431	[1]	750,947
CASH AND CASH EQUIVALENTS AT MARCH 31	$ 997,424		$ 589,334

[1] The balance sheet at December 31, 2012, has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.