Accounting for Shared-based Payments - Schedule of Stock Option Activity (Details) - Stock Options - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Weighted Average Remaining Contractual Term
Number of stock options which vest upon a change of control (in shares)	2,159,500
$0.44-9.12
Number of Options
Balance outstanding, beginning of period (in shares)		27,867,171
Balance outstanding, end of period (in shares)		28,810,791	27,867,171
Exercisable at the end of the period (in shares)		20,041,157
Exercise Price Per Share
Exercise price, low end of the range (in dollars per share)		$ 0.44	$ 0.44
Exercise price, high end of the range (in dollars per share)		9.12	9.12
Weighted Average Exercise Price Per Share
Balance outstanding, beginning of period (in dollars per share)		3.78
Balance outstanding, end of period (in dollars per share)		3.89	$ 3.78
Exercisable at the end of the period (in dollars per share)		$ 4.36
Intrinsic Value
Outstanding		$ 7,936	$ 65,618
Exercisable, end of period		$ 7,936
Weighted Average Remaining Contractual Term
Balance		6 years 2 months 9 days	7 years 1 month 6 days
Exercisable at the end of the period		5 years 1 month 10 days
$3.79
Number of Options
Granted (in shares)		2,133,000
Exercise Price Per Share
Exercise price, high end of the range (in dollars per share)		$ 3.79
Weighted Average Exercise Price Per Share
Granted (in dollars per share)		$ 4.93
$0.50-5.34
Number of Options
Exercised (in shares)		(99,978)
Exercise Price Per Share
Exercise price, low end of the range (in dollars per share)		$ 0.5
Exercise price, high end of the range (in dollars per share)		5.34
Weighted Average Exercise Price Per Share
Exercised (in dollars per share)		$ 5.48
Intrinsic Value
Exercised		$ 201
$2.61-7.91
Number of Options
Forfeited (in shares)		(1,089,402)
Exercise Price Per Share
Exercise price, low end of the range (in dollars per share)		$ 2.61
Exercise price, high end of the range (in dollars per share)		7.91
Weighted Average Exercise Price Per Share
Forfeited (in dollars per share)		$ 4.64