Segment Information - Selected Financial Data (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Revenue	$ 297,618	$ 234,995	$ 503,473	$ 444,305
Depreciation and amortization	(29,778)	(24,351)	(54,630)	(49,344)
Stock-based compensation expense	(14,372)	(7,705)	(20,957)	(14,067)
Corporate and unallocated expenses	(36,141)	(21,498)	(60,803)	(41,512)
Interest, net	(12,326)	(6,975)	(20,907)	(13,596)
Other, net	1,402	(1,677)	(510)	(1,732)
Loss before income taxes	(16,806)	(10,810)	(55,392)	(34,190)
Operating Segments | ACI On Premise
Segment Reporting Information [Line Items]
Revenue	125,119	121,395	221,126	226,425
Segment Adjusted EBITDA	57,069	54,760	85,337	93,658
Depreciation and amortization	(3,019)	(2,849)	(6,049)	(5,824)
Stock-based compensation expense	(2,051)	(1,838)	(4,007)	(3,305)
Operating Segments | ACI On Demand
Segment Reporting Information [Line Items]
Revenue	172,499	113,600	282,347	217,880
Segment Adjusted EBITDA	17,340	(3,364)	17,078	(7,597)
Depreciation and amortization	(8,489)	(7,826)	(16,051)	(15,562)
Stock-based compensation expense	(2,214)	(1,834)	(4,165)	(3,297)
Corporate and Other
Segment Reporting Information [Line Items]
Depreciation and amortization	(18,270)	(13,676)	(32,530)	(27,958)
Stock-based compensation expense	$ (10,107)	$ (4,033)	$ (12,785)	$ (7,465)