Investment in Joint Ventures Partnership's investments (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Joint Venture Activities [Roll Forward]
Investment in Joint Ventures, beginning of year				$ 4,239,485					$ 4,239,485
Equity in income of Joint Ventures	(4,588)	3,269	79,832	75,814	72,298	59,833	540,268	48,095	154,327	720,494	(185,621)
Contributions to Joint Ventures									0	253,699	753,291
Distributions from Joint Ventures									(389,332)	(519,835)	(513,767)
Investments in Joint Ventures, end of year	4,109,865				4,239,485				4,109,865	4,239,485
Fund VIII-IX Associates
Schedule of Equity Method Investments [Line Items]
Ownership in joint venture (percent)	45.20%				45.20%				45.20%	45.20%
Joint Venture Activities [Roll Forward]
Investments in Joint Ventures, end of year	4,109,865				4,239,485				4,109,865	4,239,485
Joint Ventures
Joint Venture Activities [Roll Forward]
Investment in Joint Ventures, beginning of year				4,239,485				7,186,841	4,239,485	7,186,841
Equity in income of Joint Ventures									154,327	720,494
Contributions to Joint Ventures									0	253,699
Distributions from Joint Ventures									(283,947)	(3,921,549)
Investments in Joint Ventures, end of year	$ 4,109,865				$ 4,239,485				$ 4,109,865	$ 4,239,485