Fair value measurements (Details 1) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Balance as of December 31, 2011			$ 6,634,598
Equity in earnings of OC-BVI	44,823	88,978	101,761	632,472
Distribution of earnings from OC-BVI			507,525	202,631
Balance as of June 30, 2012	6,342,459		6,342,459
Fair Value, Inputs, Level 3 [Member]
Balance as of December 31, 2011			6,634,598
Equity in earnings of OC-BVI			101,761
Distribution of earnings from OC-BVI			(393,900)
Balance as of June 30, 2012	$ 6,342,459		$ 6,342,459