Non-controlling interests (Details Textual) (Fujian Qiaolong [Member], USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2014
Fujian Qiaolong [Member]
Noncontrolling Interest [Line Items]
Noncontrolling Interest Increase Decrease from Business Combination Fair Value	$ 2.8
Fujian Qiaolong Acquisition [Member]	51.00%

Percentage of voting equity interests acquired at the acquisition date in the business combination.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

Name:	us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant