Stockholders' Equity - Additional Information (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Stockholders Equity Note Disclosure [Line Items]
Common stock, voting rights	Holders of shares of Class A common stock and Class B common stock vote together as a single class on all matters (including the election of directors) except for specific circumstances that would adversely affect the powers, preferences, or rights of a particular class of common stock.
Common stock, conversion basis	each share of Class B common stock will convert automatically to Class A common stock upon: (i) the date specified by an affirmative vote or written consent of holders of at least 67% of the outstanding shares of Class B common stock, or (ii) the seven year anniversary of the closing date of the IPO (October 2, 2020)
Year of anniversary	7 years
Anniversary closing date of the IPO	Oct. 02, 2020
Class A common stock
Stockholders Equity Note Disclosure [Line Items]
Common stock, par or stated value per share	$ 0.0001	$ 0.0001
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, voting rights	Holders of Class A common stock are entitled to one vote per share of Class A common stock
Class B common stock
Stockholders Equity Note Disclosure [Line Items]
Common stock, par or stated value per share	$ 0.0001	$ 0.0001
Common stock, shares authorized	250,000,000	250,000,000
Common stock, voting rights	holders of Class B common stock are entitled to 10 votes per share of Class B common stock.
Percentage of written consent of shareholders	67.00%
Undesignated Preferred Stock
Stockholders Equity Note Disclosure [Line Items]
Preferred stock, par value	$ 0.0001
Preferred stock, shares authorized	100,000,000	100,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0