Additional paid-in capital (Details Textual) - USD ($) $ / shares in Units, $ in Thousands					1 Months Ended	6 Months Ended		12 Months Ended
	Oct. 13, 2014	Sep. 16, 2014	Aug. 11, 2014	Aug. 13, 2013	May. 27, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Sep. 30, 2014	Sep. 26, 2014
Additional Paid In Capital [Line Items]
Common Stock, Dividends, Per Share, Declared					$ 0.18		$ 0.18
Allocated Share-based Compensation Expense								$ 200
Share-based Compensation Arrangement By Share-based Payment Award Options Exercisable Grant Date Fair Value		$ 200		$ 200
Business Acquisition Cost Of Non Controlling Interest									$ 34,500
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests						$ 0	$ 0	$ 29,812
Director [Member]
Additional Paid In Capital [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross		22,500		22,500
Henglong [Member]
Additional Paid In Capital [Line Items]
Equity Method Investment, Ownership Percentage									100.00%	20.00%
Henglong [Member] | Private Placement [Member]
Additional Paid In Capital [Line Items]
Stock Issued During Period, Shares, Acquisitions			3,260,000
Equity Method Investment, Ownership Percentage			20.00%
Jiulong [Member]
Additional Paid In Capital [Line Items]
Equity Method Investment, Ownership Percentage									100.00%	19.00%
Jiulong [Member] | Private Placement [Member]
Additional Paid In Capital [Line Items]
Stock Issued During Period, Shares, Acquisitions			818,000
Equity Method Investment, Ownership Percentage			19.00%
Henglong and Jiulong [Member]
Additional Paid In Capital [Line Items]
Business Acquisition Cost Of Non Controlling Interest						34,500
Stock Issued During Period, Value, Acquisitions	$ 37,300
Sale of Stock, Price Per Share	$ 9.15
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, before Tax, Portion Attributable to Noncontrolling Interest						4,700
Redeemable Noncontrolling Interest, Equity, Common, Fair Value						37,300
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount						34,500
Payments for Repurchase of Redeemable Noncontrolling Interest						2,800
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests						4,700
Henglong and Jiulong [Member] | Noncontrolling Interest [Member]
Additional Paid In Capital [Line Items]
Adjustments to Additional Paid in Capital, Other						$ 29,800
Jiulong Machinery Electricity [Member]
Additional Paid In Capital [Line Items]
Business Combination Consideration Transferred Equity Interests Issued	4,078,000