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		8 Months Ended		12 Months Ended
		Aug. 06, 2019		Dec. 31, 2019		Dec. 31, 2019	Aug. 05, 2019		Dec. 31, 2017		Dec. 31, 2019	Dec. 31, 2018
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		0		39,604	16,341
Granted, Number of Units				0			42,933	[2]	16,341	[3]		28,708	[4]
Forfeited, Number of Units				0			0		0			0
Vested, Number of Units				(14,459)			(49,723)		0			(5,445)
Outstanding, Number of Units, Ending Balance		30,616	[1]	16,157		16,157	32,814		16,341		16,157	39,604
Number of common stock share for each share		0.933
Converted Board RSUs	[5]	30,616
Outstanding, Weighted-Average Grant Date Fair Value per unit, Beginning balance	[6]	$ 8.35		$ 5.12	[1]	$ 8.35	$ 11.36		$ 0		$ 11.36	$ 13.77
Granted, Weighted-Average Grant Date Fair Value per Unit	[6]			0			6.95	[2]	13.77	[3]		10.45	[4]
Forfeited, Weighted-Average Grant Date Fair Value per Unit	[6]			0			0		0			0
Vested, Weighted-Average Grant Date Fair Value per Unit	[6]			5.12			9.54		0			13.77
Outstanding, Weighted-Average Grant Date Fair Value per unit, Ending balance	[6]	$ 5.12	[1]	$ 5.12		$ 5.12	$ 8.35		$ 13.77		$ 5.12	$ 11.36

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

[3] The aggregate grant date fair value of Board RSUs issued in 2017 was $0.2 million based on grant date market price of $13.77 per share.

[4] The aggregate grant date fair value of Board RSUs issued in 2018 was $0.3 million based on a grant date market price of $10.45 per share.

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

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