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Convertible Preferred Shares - Schedule of Convertible Preferred Shares Activities (Detail) ¥ in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2020 CNY (¥) shares	Sep. 30, 2020 USD ($) shares	Sep. 30, 2019 CNY (¥) shares	Sep. 30, 2019 USD ($) shares
Temporary Equity [Line Items]
Stock issued during period, value, new issues | ¥	¥ 697,878
Conversion to ordinary shares upon IPO, value | ¥	3,104,177
Series A Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Opening Balance	¥ 687,482	$ 102,852	¥ 687,482	$ 102,852
Opening Balance, Shares	30,227,056	30,227,056	30,227,056	30,227,056
Stock issued during period, value, new issues | $
Conversion to ordinary shares upon IPO, value	¥ (687,482)	$ (102,852)
Conversion to ordinary shares upon IPO, shares	(30,227,056)	(30,227,056)
Closing Balance	¥ 0	$ 0	¥ 687,482	$ 102,852
Closing Balance, Shares	0	0	30,227,056	30,227,056
Series B Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Opening Balance	¥ 921,243	$ 139,407	¥ 921,243	$ 139,407
Opening Balance, Shares	30,305,212	30,305,212	30,305,212	30,305,212
Stock issued during period, value, new issues | $
Conversion to ordinary shares upon IPO, value	¥ (921,243)	$ (139,407)
Conversion to ordinary shares upon IPO, shares	(30,305,212)	(30,305,212)
Closing Balance	¥ 0	$ 0	¥ 921,243	$ 139,407
Closing Balance, Shares	0	0	30,305,212	30,305,212
Series C Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Opening Balance	¥ 1,306,633	$ 197,478	¥ 1,306,633	$ 197,478
Opening Balance, Shares	31,046,360	31,046,360	31,046,360	31,046,360
Stock issued during period, value, new issues | $
Conversion to ordinary shares upon IPO, value	¥ (1,306,633)	$ (197,478)
Conversion to ordinary shares upon IPO, shares	(31,046,360)	(31,046,360)
Closing Balance	¥ 0	$ 0	¥ 1,306,633	$ 197,478
Closing Balance, Shares	0	0	31,046,360	31,046,360
Series C-1 Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Opening Balance	¥ 188,819	$ 26,914	¥ 0	$ 0
Opening Balance, Shares	3,857,143	3,857,143	0	0
Stock issued during period, value, new issues | $
Conversion to ordinary shares upon IPO, value	¥ (188,819)	$ (26,914)
Conversion to ordinary shares upon IPO, shares	(3,857,143)	(3,857,143)
Closing Balance	¥ 0	$ 0	¥ 0	$ 0
Closing Balance, Shares	0	0	0	0

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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

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