Consolidated balance sheets (Parenthetical) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	45,000,000	45,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Class A Common Stock [Member]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	513,797,000	513,797,000
Common stock, shares issued	36,518,000	26,725,000
Common stock, shares outstanding	36,518,000	26,725,000
Class B Common Stock [Member]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	41,203,000	41,203,000
Common stock, shares issued	33,171,000	36,508,000
Common stock, shares outstanding	33,171,000	36,508,000