| Acquisition of Citizen Engagement Centers Business - Components of Intangible Assets (Details) - USD ($) $ in Thousands | Dec. 31, 2018 | Sep. 30, 2018 | 
|---|---|---|
| Finite-Lived Intangible Assets [Line Items] | ||
| Cost | $ 258,356 | $ 139,359 | 
| Accumulated Amortization | 53,803 | 51,324 | 
| Intangible Assets, net | 204,553 | 88,035 | 
| Customer contracts and relationships | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Cost | 248,323 | 129,113 | 
| Accumulated Amortization | 45,273 | 42,683 | 
| Intangible Assets, net | 203,050 | 86,430 | 
| Technology based intangible assets | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Cost | 5,564 | 5,750 | 
| Accumulated Amortization | 4,113 | 4,212 | 
| Intangible Assets, net | 1,451 | 1,538 | 
| Trademarks and trade names | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Cost | 4,469 | 4,496 | 
| Accumulated Amortization | 4,417 | 4,429 | 
| Intangible Assets, net | $ 52 | $ 67 | 
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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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