Equity-based Awards - Summary of Information Regarding Restricted Stock Unit Awards (Detail) - $ / 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
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		614,754		598,024	682,792
Granted, Number of Units				17,500	[1]		300,517	[2]	173,070	[3]		437,000	[4]
Forfeited, Number of Units				(38,652)			(38,151)		(105,032)			(363,513)	[5]
Vested, Number of Units				(81,723)			(437,834)		0			(158,255)
Outstanding, Number of Units, Ending Balance		394,245	[1]	291,370		291,370	422,556		682,792		291,370	598,024
Merger conversion ratio	[6],[7]	0.933
Converted TSUs		394,245
Outstanding, Weighted-Average Grant Date Fair Value per unit, Beginning balance	[8]	$ 10.87		$ 5.12	[9]	$ 10.87	$ 11.35		$ 13.77		$ 11.35	$ 13.54
Granted, Weighted-Average Grant Date Fair Value per Unit	[8]			6.14			6.80	[2]	12.87	[3]		10.51	[4]
Forfeited, Weighted-Average Grant Date Fair Value per Unit	[8]			5.12			11.13		13.77			13.55	[5]
Vested, Weighted-Average Grant Date Fair Value per Unit	[8]			5.12			8.71		0			13.44
Outstanding, Weighted-Average Grant Date Fair Value per unit, Ending balance	[8]	$ 5.12	[9]	$ 5.18		$ 5.18	$ 10.87		$ 13.54		$ 5.18	$ 11.35
Number of common stock share for each share	[6],[7]	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	[10]	388,500	393,500				393,500	0
Granted, Number of Units				17,500			17,750	[11]				395,500	[12]
Forfeited, Number of Units				(74,078)			(22,750)					(2,000)
Vested, Number of Units				0			0					0
Outstanding, Number of Units, Ending Balance		362,471	[10]	305,893		305,893	388,500		0		305,893	393,500
Merger conversion ratio	[13],[14]	0.933
Converted TSUs		362,471
Outstanding, Weighted-Average Grant Date Fair Value per unit, Beginning balance	[15]	$ 7.98		$ 2.11	[16]	$ 7.98	$ 8.14				$ 8.14	$ 0
Granted, Weighted-Average Grant Date Fair Value per Unit	[15]			2.87			4.06	[11]				8.14	[12]
Forfeited, Weighted-Average Grant Date Fair Value per Unit	[15]			2.11			7.59					7.59
Vested, Weighted-Average Grant Date Fair Value per Unit	[15]			0			0					0
Outstanding, Weighted-Average Grant Date Fair Value per unit, Ending balance	[15]	$ 2.11	[16]	$ 2.15		$ 2.15	$ 7.98		$ 0		$ 2.15	$ 8.14
Number of common stock share for each share	[13],[14]	0.933

[1] 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

[2] 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.

[3] The aggregate grant date fair value of TSUs issued for the period from May 5, 2017 through December 31, 2017 was $2.2 million based on a grant date market price ranging from $10.00 to $13.77 per share.

[4] The aggregate grant date fair value of TSUs issued for the year ended December 31, 2018 was $4.6 million based on a grant date market price ranging from $9.30 to $11.00 per share.

[5] Certain Legacy Amplify departing executives forfeited 298,354 TSUs during the year ended December 31, 2018, in connection with their separation and retirement agreements.

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

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

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

[9] 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

[10] 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

[11] 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.

[12] The aggregate grant date fair value of PSUs issued for the year ended December 31, 2018 was $3.2 million based on a calculated fair value price ranging from $5.88 to $9.87 per share.

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

[14] 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

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

[16] 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