Segment Information - Selected Financial Data (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 205,855	$ 209,310
Depreciation and amortization expense	(24,852)	(24,993)
Stock-based compensation expense	(6,585)	(6,362)
Corporate and unallocated expenses	(24,662)	(20,014)
Interest, net	(8,581)	(6,621)
Other, net	(1,912)	(55)
Income (loss) before income taxes	(38,586)	(23,380)
Operating Segments [Member] \| ACI On Premise [Member]
Segment Reporting Information [Line Items]
Revenues	96,007	105,030
Segment Adjusted EBITDA	28,268	38,898
Depreciation and amortization expense	3,030	2,975
Stock-based compensation expense	1,956	1,467
Operating Segments [Member] \| ACI On Demand [Member]
Segment Reporting Information [Line Items]
Revenues	109,848	104,280
Segment Adjusted EBITDA	(262)	(4,233)
Depreciation and amortization expense	7,562	7,736
Stock-based compensation expense	1,951	1,463
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization expense	14,260	14,282
Stock-based compensation expense	$ 2,678	$ 3,432

Other operating expenses related to corporate functions and not allocated to reportable segments.

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Segment Adjusted EBITDA is defined as earnings (loss) from operations before interest, income tax expense (benefit), depreciation and amortization adjusted to exclude stock-based compensation and net other income (expense).

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The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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The net amount of operating interest income (expense).

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Amount of income (expense) related to nonoperating activities, classified as other.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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