Fair value measurements (Details 1) - USD ($)		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Investment in OC-BVI
Balance as of December 31, 2015		$ 4,548,271
Impairment of investment in OC-BVI (See Note 7)		50,000	$ 310,000
Balance as of March 31, 2016		4,578,060
Net liability arising from put/call options
Balance as of March 31, 2016		383,000
Fair Value, Inputs, Level 3 [Member]
Investment in OC-BVI
Balance as of December 31, 2015		4,548,271
Profit sharing and equity from earnings of OC-BVI		79,789
Distributions received from OC-BVI		0
Impairment of investment in OC-BVI (See Note 7)		(50,000)
Balance as of March 31, 2016		4,578,060
Net liability arising from put/call options
Balance as of December 31, 2015	[1]	0
Net liability arising from put/call options	[1]	383,000
Balance as of March 31, 2016	[1]	$ 383,000

[1] The net liability arising from put/call options is included in the accompanying condensed consolidated balance sheets within other liabilities as of March 31, 2016.