Fair Value Measurement (Details 1) $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($)
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
December 31, 2014
Net realized \ unrealized gain	$ 2,611
Issuance	$ (3,108)
Transfers out of (into) Level 3
Settlements	$ 2,206
September 30, 2015	(497)
Unrealized gain- still held	405
Level 3 [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
September 30, 2015	$ 497
Level 3 [Member] | Derivative options based on equity shares [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
December 31, 2014
Net realized \ unrealized gain	$ 1,930
Issuance	$ (2,297)
Transfers out of (into) Level 3
Settlements	$ 1,630
September 30, 2015	(367)
Unrealized gain- still held	$ 300
Level 3 [Member] | Derivative options based on commodities [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
December 31, 2014
Net realized \ unrealized gain	$ 130
Issuance	$ (155)
Transfers out of (into) Level 3
Settlements	$ 110
September 30, 2015	(25)
Unrealized gain- still held	$ 20
Level 3 [Member] | Derivative options based on exchange differences [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
December 31, 2014
Net realized \ unrealized gain	$ 551
Issuance	$ (656)
Transfers out of (into) Level 3
Settlements	$ 466
September 30, 2015	(105)
Unrealized gain- still held	$ 85