Share Options - Stock Option Outstanding Separated into Ranges of Exercise Prices (Details) - $ / shares	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Number of options outstanding	9,950,498	7,426,159
Options outstanding, weighted average remaining contractual term	6 years 7 months 13 days
Number of options exercisable	5,163,286
Options exercisable, weighted average remaining contractual term	4 years 7 months 17 days
Exercise price 0.01
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 0.01
Number of options outstanding	98,995
Options outstanding, weighted average remaining contractual term	5 months 16 days
Number of options exercisable	98,995
Options exercisable, weighted average remaining contractual term	5 months 16 days
Exercise price 0.17
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 0.17
Number of options outstanding	1,403,857
Options outstanding, weighted average remaining contractual term	11 months 16 days
Number of options exercisable	1,403,857
Options exercisable, weighted average remaining contractual term	11 months 16 days
Exercise price 0.23
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 0.23
Number of options outstanding	440,531
Options outstanding, weighted average remaining contractual term	3 years 8 months 5 days
Number of options exercisable	440,531
Options exercisable, weighted average remaining contractual term	3 years 8 months 5 days
Exercise price 0.38
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 0.38
Number of options outstanding	488,331
Options outstanding, weighted average remaining contractual term	5 years 15 days
Number of options exercisable	488,331
Options exercisable, weighted average remaining contractual term	5 years 15 days
Exercise price 3.44
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 3.44
Number of options outstanding	1,779,072
Options outstanding, weighted average remaining contractual term	6 years 1 month 17 days
Number of options exercisable	1,350,491
Options exercisable, weighted average remaining contractual term	6 years 1 month 13 days
Exercise price 6.72
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 6.72
Number of options outstanding	940,424
Options outstanding, weighted average remaining contractual term	6 years 11 months 5 days
Number of options exercisable	687,525
Options exercisable, weighted average remaining contractual term	6 years 11 months 5 days
Exercise price 6.83
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 6.83
Number of options outstanding	92,227
Options outstanding, weighted average remaining contractual term	7 years 2 months 12 days
Number of options exercisable	46,390
Options exercisable, weighted average remaining contractual term	7 years 2 months 12 days
Exercise price 7.03
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 7.03
Number of options outstanding	613,174
Options outstanding, weighted average remaining contractual term	7 years 4 months 21 days
Number of options exercisable	306,570
Options exercisable, weighted average remaining contractual term	7 years 4 months 21 days
Exercise price 7.04
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 7.04
Number of options outstanding	137,321
Options outstanding, weighted average remaining contractual term	7 years 8 months 19 days
Number of options exercisable	69,311
Options exercisable, weighted average remaining contractual term	7 years 8 months 19 days
Exercise price 7.28
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 7.28
Number of options outstanding	167,921
Options outstanding, weighted average remaining contractual term	7 years 10 months 24 days
Number of options exercisable	79,366
Options exercisable, weighted average remaining contractual term	7 years 10 months 24 days
Exercise price 7.48
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 7.48
Number of options outstanding	504,365
Options outstanding, weighted average remaining contractual term	8 years 4 months 21 days
Number of options exercisable	127,555
Options exercisable, weighted average remaining contractual term	8 years 4 months 21 days
Exercise price 7.52
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 7.52
Number of options outstanding	116,769
Options outstanding, weighted average remaining contractual term	8 years 5 months 27 days
Number of options exercisable	29,186
Options exercisable, weighted average remaining contractual term	8 years 5 months 27 days
Exercise price 7.58
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 7.58
Number of options outstanding	52,032
Options outstanding, weighted average remaining contractual term	8 years 8 months 27 days
Number of options exercisable	13,006
Options exercisable, weighted average remaining contractual term	8 years 8 months 27 days
Exercise price 7.73
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 7.73
Number of options outstanding	431,053
Options outstanding, weighted average remaining contractual term	9 years 7 days
Number of options exercisable	22,172
Options exercisable, weighted average remaining contractual term	8 years 10 months 13 days
Exercise price 14.37
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 14.37
Number of options outstanding	1,616,012
Options outstanding, weighted average remaining contractual term	9 years 4 months 28 days
Exercise price 15.60
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 15.60
Number of options outstanding	146,926
Options outstanding, weighted average remaining contractual term	9 years 6 months 26 days
Exercise price 22.00
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise price	$ 22.00
Number of options outstanding	921,488
Options outstanding, weighted average remaining contractual term	10 years