Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements (Details 6) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Convertible Note 2019
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stated interest rate	3.75%	3.75%
Face amount of the Notes	$ 68,660,000	$ 143,750,000
Convertible Note 2023
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stated interest rate	4.75%	4.75%
Face amount of the Notes	$ 75,090,000