Share-based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Assumptions Used to Estimate Fair Values of Share Options Granted

The following table presents the assumptions used to estimate the fair values of the share options granted in the years presented:

	May 2017			September 2017			2018			2019
Risk-free rate of return		3.2	%		3.5	%	2.7%-3.2%			1.6%-2.5%
Contractual life of option	10 years			10 years			10 years			10 years
Expected term	n/a			n/a			6.5 years			6 or 6.5 years
Estimated volatility rate		70	%		70	%		70	%		70	%
Expected dividend yield		0	%		0	%		0	%		0	%
Fair value of underlying ordinary shares		9.60			27.93		17.60-24.58			27.23-41.59

Summary of Option Activity

A summary of option activity under the Plan during the years ended December 31, 2017, 2018 and 2019 is presented below:

	Number of options			Weighted average exercise price		Weighted average remaining contractual term		Aggregate intrinsic value
				$		Years		$
Outstanding at January 1, 2017		7,228,141			0.97		9.00		53,677,170
Granted		264,480			8.76		—		—
Exercised		(100,834	)		0.65		—		—
Forfeited		(843,410	)		1.11		—		—
Outstanding at December 31, 2017		6,548,377			1.28		8.06		130,668,851
Granted		2,759,750			21.15		—		—
Exercised		(256,065	)		0.76		—		—
Forfeited		(290,327	)		3.73		—		—
Outstanding at December 31, 2018		8,761,735			7.47		7.80		138,009,758
Granted		1,067,385			32.22		—		—
Exercised		(670,939	)		1.57		—		—
Forfeited		(35,201	)		25.99		—		—
Outstanding at December 31, 2019		9,122,980			10.73		7.16		281,562,301
Vested and Exercisable as of December 31, 2019		4,379,511			3.51		6.25		166,772,005
Vested or expected to vest as of December 31, 2019		9,122,980			10.73		7.16		281,562,301

Allocation of Compensation Expense Related to Option

The weighted-average grant-date fair value of the options granted in 2017, 2018 and 2019 were $13.92, $14.03 and $20.98 per share, respectively. The Group recorded compensation expense related to the options of $4,752, $9,403 and $14,925 for the years ended December 31, 2017, 2018 and 2019, respectively, which were classified in the accompanying consolidated statements of operations as follows:

	Year ended December 31,
	2017		2018		2019
	$		$		$
Selling, general and administrative		2,215		4,428		6,931
Research and development		2,537		4,975		7,994
Total		4,752		9,403		14,925

Summary of Non-vested Restricted Share Activity

The following table summarized the Group’s non-vested restricted share activity in 2019:

	Numbers of non-vested restricted shares			Weighted average grant date fair value
				$
Non-vested as of January 1, 2018		693,333			2.57
Granted		757,000			20.73
Vested		(338,332	)		1.95
Non-vested as of December 31, 2018		1,112,001			15.13
Granted		171,000			27.55
Vested		(539,733	)		8.97
Non-vested as of December 31, 2019		743,268			22.45

Allocation of Compensation Expense Related to Restricted Shares

As of December 31, 2019, there was $13,730 of total unrecognized compensation expense related to non-vested restricted shares. The Group recorded compensation expense related to the restricted shares of $5,179, $2,826 and $5,366 for the years ended December 31, 2017, 2018 and 2019, respectively, which were classified in the accompanying consolidated statements of operations as follows:

	Year ended December 31,
	2017		2018		2019
	$		$		$
Selling, general and administrative		3,848		2,206		3,643
Research and development		1,331		620		1,723
Total		5,179		2,826		5,366