Income Tax - Changes in valuation allowances (Details 5) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax - Changes In Valuation Allowances Details 5
Credited / (charged) to income tax expense	$ 3,606	$ 153	$ (84)

Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 45

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=37586315&loc=d3e32123-109318

Name:	us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration