Fair Value Measurement - Narrative (Details) - USD ($) $ in Millions |
Dec. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Fixed-Rate Long-term Debt | ||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
| Long term debt, carrying value | $ 180.0 | $ 265.0 |