Acquisition of Citizen Engagement Centers Business - Components of Intangible Assets (Details) - USD ($) $ in Thousands  | 
Jun. 30, 2019  | 
Sep. 30, 2018  | 
|---|---|---|
| Finite-Lived Intangible Assets [Line Items] | ||
| Cost | $ 258,493 | $ 139,359 | 
| Accumulated Amortization | 72,528 | 51,324 | 
| Intangible Assets, net | 185,965 | 88,035 | 
| Customer contracts and relationships | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Cost | 248,324 | 129,113 | 
| Accumulated Amortization | 63,684 | 42,683 | 
| Intangible Assets, net | 184,640 | 86,430 | 
| Technology based intangible assets | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Cost | 5,680 | 5,750 | 
| Accumulated Amortization | 4,385 | 4,212 | 
| Intangible Assets, net | 1,295 | 1,538 | 
| Trademarks and trade names | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Cost | 4,489 | 4,496 | 
| Accumulated Amortization | 4,459 | 4,429 | 
| Intangible Assets, net | $ 30 | $ 67 | 
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- Definition Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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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 after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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