| Acquisition of Citizen Engagement Centers Business - Schedule of the Valuation of the Intangible Assets Acquired (Details) - General Dynamics Information Technology's Citizen Engagement Centers $ in Thousands | 3 Months Ended | 
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| Dec. 31, 2018  USD ($) | |
| Finite-Lived Intangible Assets [Line Items] | |
| Fair value | $ 122,300 | 
| Customer relationships - all contracts except U.S. Census | |
| Finite-Lived Intangible Assets [Line Items] | |
| Useful life | 10 years | 
| Fair value | $ 85,300 | 
| Customer relationships - U.S. Census | |
| Finite-Lived Intangible Assets [Line Items] | |
| Useful life | 2 years | 
| Fair value | $ 37,000 | 
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- Definition Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. No definition available. 
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- Definition 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. No definition available. 
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- Definition Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, from an acquisition. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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