UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Redeemable Series D convertible preferred stock, redemption amount	$ 290,491,100	$ 280,650,800
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	50,969,841	50,969,841
Common stock, shares outstanding	50,969,841	50,948,841
Treasury shares, shares	21,000	21,000