Accounting for Shared-based Payments - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Weighted Average Remaining Contractual Term
Proceeds from exercise of stock options		$ 300	$ 347	$ 23
Stock Options
Weighted Average Remaining Contractual Term
Number of stock options which vest upon a change of control (in shares)	2,159,500
Stock Options | $0.44-9.12
Number of Options
Balance outstanding, beginning of period (in shares)			27,867,171
Balance outstanding, end of period (in shares)	28,882,068	28,882,068	28,882,068		27,867,171
Exercisable at the end of the period (in shares)	19,238,509	19,238,509	19,238,509
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)	$ 3.90	$ 3.90	3.90		$ 3.78
Exercisable at the end of the period (in dollars per share)	$ 3.49	$ 3.49	$ 3.49
Intrinsic Value
Outstanding	$ 27,677	$ 27,677	$ 27,677		$ 65,618
Exercisable, end of period	$ 23,650	$ 23,650	$ 23,650
Weighted Average Remaining Contractual Term
Balance			6 years 9 months 18 days		7 years 1 month 6 days
Exercisable at the end of the period			5 years 8 months 27 days
Stock Options | $3.63-6.77
Number of Options
Granted (in shares)			2,055,500
Exercise Price Per Share
Exercise price, low end of the range (in dollars per share)			$ 3.63
Exercise price, high end of the range (in dollars per share)			6.77
Weighted Average Exercise Price Per Share
Granted (in dollars per share)			$ 4.98
Stock Options | $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)			$ 3.47
Intrinsic Value
Exercised			$ 226,757
Stock Options | $2.83-7.91
Number of Options
Forfeited (in shares)			(940,625)
Exercise Price Per Share
Exercise price, low end of the range (in dollars per share)			$ 2.83
Exercise price, high end of the range (in dollars per share)			7.91
Weighted Average Exercise Price Per Share
Forfeited (in dollars per share)			$ 4.52