Equity-based Awards - Summary of Information Regarding Restricted Stock Awards (Detail) - Restricted Stock Units (RSUs) - 2017 Non-Employee Directors Compensation Plan [Member] - $ / shares				5 Months Ended			7 Months Ended		12 Months Ended
		Aug. 06, 2019		Dec. 31, 2019		Dec. 31, 2019	Aug. 05, 2019		Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding, Number of Units, Beginning Balance		32,814		30,616	[1]	32,814	39,604		16,157	39,604
Granted, Number of Units				0			42,933	[2]	0
Forfeited, Number of Units				0			0		0
Vested, Number of Units				(14,459)			(49,723)		(7,259)
Outstanding, Number of Units, Ending Balance		30,616	[1]	16,157		16,157	32,814		8,898	16,157
Merger conversion ratio	[3]	0.933
Converted Board RSUs		30,616
Outstanding, Weighted-Average Grant Date Fair Value per unit, Beginning balance	[4]	$ 8.35		$ 5.12	[1]	$ 8.35	$ 11.36		$ 5.12	$ 11.36
Granted, Weighted-Average Grant Date Fair Value per Unit	[4]			0			6.95	[2]	0
Forfeited, Weighted-Average Grant Date Fair Value per Unit	[4]			0			0		0
Vested, Weighted-Average Grant Date Fair Value per Unit	[4]			5.12			9.54		5.12
Outstanding, Weighted-Average Grant Date Fair Value per unit, Ending balance	[4]	$ 5.12	[1]	$ 5.12		$ 5.12	$ 8.35		$ 5.12	$ 5.12

[1] This reflects the unvested Board RSU awards converted into newly issued Board RSUs at August 6, 2019 in which the stock price was at $5.12 per share.

[2] The aggregate grant date fair value of Board RSUs issued for the period from January 1, 2019 through August 5, 2019 was $0.3 million based on a grant date market price of $6.95 per share.

[3] The merger ratio used to convert Legacy Amplify Board RSUs into newly issued Company Board RSUs.

[4] Determined by dividing the aggregate grant date fair value of awards by the number of awards issued.