Schedule II - Valuation and Qualifying Accounts: (Details 1) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Cost Basis
Balance at beginning of year	$ 38,818,011	$ 38,400,335
Additions	207,239	817,636
Disposals	0	(399,960)
Balance at end of year	39,025,250	38,818,011
Accumulated depreciation
Balance at beginning of year	31,062,484	29,718,564
Depreciation	1,409,210	1,743,880
Disposals	0	(399,960)
Balance at end of year	$ 32,471,694	$ 31,062,484