Schedule II - Valuation and Qualifying Accounts: (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Cost Basis
Balance at beginning of year	$ 34,915,538	$ 33,539,000
Additions	2,229,000	1,377,000
Disposals	0	0
Balance at end of year	36,571,114	34,915,538
Accumulated depreciation
Balance at beginning of year	26,072,000	24,486,000
Depreciation	1,800,000	1,586,000
Disposals	0	0
Balance at end of year	$ 27,872,000	$ 26,072,000