Stockholders' Equity - Additional Information (Detail) - shares		1 Months Ended	3 Months Ended	12 Months Ended
	Apr. 04, 2017	Apr. 21, 2017	Sep. 30, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Common stock, voting rights			Holders of the Company's common stock are entitled to one vote for each share of common stock.
Preferred stock, shares authorized			1,000,000	1,000,000
Preferred stock, shares issued			0	0
Preferred stock, shares outstanding			0	0
IPO [Member]
Class of Stock [Line Items]
Number of units issued in public offering	35,000,000	37,732,112
Class A Common Stock [Member]
Class of Stock [Line Items]
Common stock, shares authorized			200,000,000	200,000,000
Common stock shares outstanding including shares which are subject to redemption			37,732,112	37,732,112
Shares subject to redemption			36,061,344	36,026,954
Common stock, shares issued			1,670,768	1,705,158
Common stock, shares outstanding			1,670,768	1,705,158
Class A Common Stock [Member] | IPO [Member]
Class of Stock [Line Items]
Number of units issued in public offering			37,732,112	37,732,112
Class B Common Stock [Member]
Class of Stock [Line Items]
Common stock, shares authorized			20,000,000
Common stock, shares issued			9,433,028	9,433,028
Common stock, shares outstanding			9,433,028	9,433,028