Condensed Statements Of Cash Flows (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Cash flows from operating activities:
Cash received from royalties and rents	$ 4,999,630	$ 4,363,142
Cash paid to suppliers and employees	(764,688)	(712,325)
Interest received	12,457	28,176
NET CASH PROVIDED BY OPERATING ACTIVITIES	4,247,399	3,678,993
Cash flows from investing activities:
United States Treasury securities purchased	(2,725,000)	(675,000)
United States Treasury securities matured	2,825,000	5,225,000
NET CASH PROVIDED BY INVESTING ACTIVITIES	100,000	4,550,000
Cash flows from financing activities:
Distributions paid	(3,975,000)	(7,875,000)
NET CASH USED IN FINANCING ACTIVITIES	(3,975,000)	(7,875,000)
Net increase in cash and cash equivalents	372,399	353,993
Cash and cash equivalents at beginning of year	712,197	643,431
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 1,084,596	$ 997,424