Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Unrecognized cost of unvested options awarded to employees as compensation.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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Gross number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Percentage of vesting of share-based compensation awards.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Share-based Compensation - Share Options - Additional Information (Details) - USD ($)	1 Months Ended					12 Months Ended
	Sep. 30, 2017	May 31, 2017	Dec. 31, 2016	Aug. 31, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 05, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized									4,140,945
Options granted						2,759,750	264,480	2,918,993
Exercise price of options						$ 21.15	$ 8.76	$ 1.53
Weighted-average grant-date fair value of options granted						$ 14.03	$ 13.92	$ 6.94
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense						$ 9,403,059	$ 4,751,933	$ 3,524,733
Unrecognized compensation expense related to unvested share options granted						$ 46,006,585
Recognized over a weighted-average period						2 years 9 months 18 days
Management and Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted		158,313		1,760,368	1,157,793
Exercise price of options		$ 3.0		$ 1.74	$ 1.2
Options granted contractual term		10 years		10 years	10 years
Vesting period				5 years	5 years
Management and Employees \| Two Thousand Seventeen Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted	101,584					2,759,750
Exercise price of options	$ 18.0
Options granted contractual term	10 years					10 years
Vesting period	5 years					5 years
Management and Employees \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		4 years
Management and Employees \| Minimum \| Two Thousand Seventeen Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price of options						$ 17.60
Management and Employees \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		5 years
Management and Employees \| Maximum \| Two Thousand Seventeen Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price of options						$ 24.58
Management and Employees \| Vesting anniversary year after the grant date
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option vesting percentage				20.00%	20.00%
Management and Employees \| Vesting anniversary year after the grant date \| Two Thousand Seventeen Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option vesting percentage	20.00%					20.00%
Management and Employees \| Vesting anniversary year after the grant date \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option vesting percentage		25.00%
Management and Employees \| Vesting anniversary year after the grant date \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option vesting percentage		20.00%
Individual Advisors
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted		4,583	416	416
Exercise price of options		$ 3.0	$ 1.74	$ 1.74
Options granted contractual term		10 years	10 years	10 years
Vesting period		3 years	3 years	3 years
Individual Advisors \| Vesting anniversary year after the grant date
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option vesting percentage		33.33%	33.33%	33.33%