Intangible assets, net (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Intangible assets, net [Abstract]
Intangible assets	$ 52,562		$ 52,562
Accumulated amortization	(16,342)		(13,714)
Intangible assets, net	$ 36,220		$ 38,848
Intangible assets, useful life	10 years
Amortization of intangible assets	$ 2,628	$ 2,736