Equity-based Awards - Summary of Information Regarding Restricted Stock Unit Awards (Detail) - $ / 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
TSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding, Weighted-Average Grant Date Fair Value per unit, Beginning balance				$ 5.12
Outstanding, Weighted-Average Grant Date Fair Value per unit, Ending balance		$ 5.12
Management Incentive Plan [Member] | TSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding, Number of Units, Beginning Balance		422,556		394,245	[1]	422,556	598,024		291,370		598,024
Granted, Number of Units				17,500	[2]		300,517	[3]	43,250	[4]
Forfeited, Number of Units				(38,652)			(38,151)		(93,845)
Vested, Number of Units				(81,723)			(437,834)		(124,978)
Outstanding, Number of Units, Ending Balance		394,245	[1]	291,370		291,370	422,556		115,797		291,370
Merger conversion ratio	[5]	0.933
Converted TSUs		394,245
Outstanding, Weighted-Average Grant Date Fair Value per unit, Beginning balance	[6]	$ 10.87		$ 5.12	[1]	$ 10.87	$ 11.35		$ 5.18		$ 11.35
Granted, Weighted-Average Grant Date Fair Value per Unit	[6]			6.14	[2]		6.80	[3]	3.10	[4]
Forfeited, Weighted-Average Grant Date Fair Value per Unit	[6]			5.12			11.13		5.12
Vested, Weighted-Average Grant Date Fair Value per Unit	[6]			5.12			8.71		5.17
Outstanding, Weighted-Average Grant Date Fair Value per unit, Ending balance	[6]	$ 5.12	[1]	$ 5.18		$ 5.18	$ 10.87		$ 4.47		$ 5.18
Merger conversion ratio	[5]	0.933
Management Incentive Plan [Member] | PSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding, Number of Units, Beginning Balance		388,500		362,471	[7]	388,500	393,500		305,893		393,500
Granted, Number of Units				17,500	[8]		17,750	[9]	43,250	[10]
Forfeited, Number of Units				(74,078)			(22,750)		(134,589)
Vested, Number of Units				0			0		0
Outstanding, Number of Units, Ending Balance		362,471	[7]	305,893		305,893	388,500		214,554		305,893
Merger conversion ratio	[11]	0.933
Converted TSUs		362,471
Outstanding, Weighted-Average Grant Date Fair Value per unit, Beginning balance	[6]	$ 7.98		$ 2.11	[7]	$ 7.98	$ 8.14		$ 2.15		$ 8.14
Granted, Weighted-Average Grant Date Fair Value per Unit	[6]			2.87	[8]		4.06	[9]	3.03	[10]
Forfeited, Weighted-Average Grant Date Fair Value per Unit	[6]			2.11			7.59		2.11
Vested, Weighted-Average Grant Date Fair Value per Unit	[6]			0			0		0
Outstanding, Weighted-Average Grant Date Fair Value per unit, Ending balance	[6]	$ 2.11	[7]	$ 2.15		$ 2.15	$ 7.98		$ 2.36		$ 2.15
Merger conversion ratio	[11]	0.933

[1] This reflects the unvested TSUs converted into newly issued Company’s TSUs at August 6, 2019 at a stock price of $5.12 per share.

[2] The aggregate grant date fair value of TSUs issued for the period August 6, 2019 through December 31, 2019 was $0.1 million based on a grant date market price of $6.14 per share.

[3] The aggregate grant date fair value of TSUs issued for the period from January 1, 2019 through August 5, 2019 was $2.0 million based on a grant date market price ranging from $4.48 to $8.70 per share.

[4] The aggregate grant date fair value of TSUs issued for the year ended December 31, 2020 was $0.1 million based on a grant date market price ranging from $0.54 to $6.61 per share.

[5] The merger ratio used to convert Legacy Amplify TSUs into newly issued TSUs.

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

[7] This reflects the unvested PSU awards converted into newly issued PSUs at August 6, 2019 based on a calculated fair value price ranging from $1.64 to $2.63 per share.

[8] The aggregate grant date fair value of PSUs issued for the period August 6, 2019 through December 31, 2019 was less than $0.1 million based on a calculated fair value price ranging from $2.38 to $3.40 per share.

[9] The aggregate grant date fair value of PSUs issued for the period January 1, 2019 through August 5, 2019 was less than $0.1 million based on a calculated fair value price ranging from $1.64 to $6.76 per share.

[10] The aggregate grant date fair value of PSUs issued for the year ended December 31, 2020 was $0.1 million based on a calculated fair value price ranging from $2.46 to $3.66 per share.

[11] The merger ratio used to convert Legacy Amplify PSUs into newly issued Company PSUs.