Summary of Significant Accounting Policies - Deferred Implementation Costs, Deferred Solution and Other Costs (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2018 |
Jun. 30, 2017 |
Jun. 30, 2018 |
Jun. 30, 2017 |
|
| Minimum | ||||
| Capitalized Contract Cost [Line Items] | ||||
| Expected period of customer benefit | 5 years | 5 years | ||
| Maximum | ||||
| Capitalized Contract Cost [Line Items] | ||||
| Expected period of customer benefit | 7 years | 7 years | ||
| Deferred Implementation Costs | ||||
| Capitalized Contract Cost [Line Items] | ||||
| Capitalization of deferred commissions | $ 1.5 | $ 1.4 | $ 3.1 | $ 2.7 |
| Amortization of capitalized deferred commissions | 1.2 | 1.1 | 2.4 | 2.0 |
| Deferred Commissions | ||||
| Capitalized Contract Cost [Line Items] | ||||
| Capitalization of deferred commissions | 1.5 | 0.7 | 3.9 | 2.1 |
| Amortization of capitalized deferred commissions | $ 0.8 | $ 0.7 | $ 1.7 | $ 1.5 |