Investments and Fair Value Measurement - Summary of Unobservable Inputs (Details) |
Sep. 30, 2019
$ / shares
|
Dec. 31, 2018
$ / shares
|
|---|---|---|
| Relative weighting | ||
| Fair Value Measurement Inputs and Valuation Techniques [Line Items] | ||
| Financing transactions, measurement input | 1 | 1 |
| Transaction price per share | ||
| Fair Value Measurement Inputs and Valuation Techniques [Line Items] | ||
| Financing transactions, measurement input | 6.16 | 6.16 |