Segment Information - Selected Financial Data (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenue	$ 315,883	$ 354,901	$ 907,278	$ 858,374
Depreciation and amortization	(35,490)	(33,913)	(105,004)	(88,543)
Stock-based compensation expense	(8,061)	(9,371)	(22,943)	(30,328)
Corporate and unallocated expenses	(28,024)	(19,512)	(71,967)	(80,315)
Interest, net	(9,998)	(15,999)	(35,457)	(36,906)
Other, net	1,356	(2,369)	(6,361)	(2,879)
Income (loss) before income taxes	22,540	36,950	7,219	(18,442)
Operating Segments | ACI On Demand
Segment Reporting Information [Line Items]
Revenue	190,369	192,952	563,892	475,299
Segment Adjusted EBITDA	33,204	18,561	89,396	35,639
Depreciation and amortization	(10,227)	(9,059)	(30,411)	(25,110)
Stock-based compensation expense	(2,255)	(2,389)	(6,554)	(6,554)
Operating Segments | ACI On Premise
Segment Reporting Information [Line Items]
Revenue	125,514	161,949	343,386	383,075
Segment Adjusted EBITDA	69,553	99,553	159,555	184,890
Depreciation and amortization	(3,312)	(2,963)	(9,849)	(9,012)
Stock-based compensation expense	(2,259)	(2,227)	(6,568)	(6,234)
Corporate and Other
Segment Reporting Information [Line Items]
Depreciation and amortization	(21,951)	(21,891)	(64,744)	(54,421)
Stock-based compensation expense	$ (3,547)	$ (4,755)	$ (9,821)	$ (17,540)