Debt and Other Obligations - Local bank loans and other short term borrowings (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Deutsche Bank AG
Debt Instrument [Line Items]
Proceeds short-term debt	$ 26,400,000	$ 28,600,000
Unicredit
Debt Instrument [Line Items]
Proceeds short-term debt	$ 2,200,000	$ 0

The cash inflow from a borrowing having initial term of repayment within one year or the normal operating cycle, if longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

Name:	us-gaap_ProceedsFromShortTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration