Accounts and notes receivable, net (Details) - USD ($) $ in Thousands		Jun. 30, 2015	Dec. 31, 2014
Financing Receivables [Line Items]
Accounts receivable - unrelated parties	[1]	$ 144,630	$ 137,165
Notes receivable - unrelated parties	[2],[3]	133,395	146,597
Total accounts and notes receivable- unrelated parties		278,025	283,762
Less: allowance for doubtful accounts - unrelated parties		(1,377)	(1,414)
Accounts and notes receivable, net - unrelated parties		276,648	282,348
Accounts and notes receivable, net - related parties		27,003	22,760
Accounts and notes receivable, net		$ 303,651	$ 305,108

[1] As of June 30, 2015 and December 31, 2014, the Company has pledged $42.6 million and $34.3 million, respectively, of accounts receivable as security for its comprehensive credit facilities with banks in China.

[2] As of June 30, 2015, Henglong collateralized its notes receivable in an amount of RMB236.8 million, equivalent to approximately $38.7 million, including RMB211.5 million, equivalent to approximately $34.6 million, as security in favor of Industrial and Commercial Bank of China, Jingzhou Branch, “ICBC Jingzhou,” for the purpose of obtaining the Henglong Standby Letter of Credit (as defined in Note 14) which is used as security for the non-revolving credit facility in the amount of $30.0 million provided by Industrial and Commercial Bank of China (Macau) Limited, “ICBC Macau”, and RMB25.3 million, equivalent to approximately $4.1 million, as security in favor of the Chinese government for the low-interest government loan (See Note 14).

[3] Notes receivable represent accounts receivable in the form of bills of exchange for which acceptances are guaranteed and settlements are handled by banks.