Income Taxes - Narrative (Details) - USD ($) |
3 Months Ended | 12 Months Ended | |
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Income Tax [Line Items] | |||
| Charge to equity in connection with issuance of shares to non-controlling interest | $ 5,600,000 | ||
| Domestic Tax Authority | |||
| Income Tax [Line Items] | |||
| Operating loss carryforwards | $ 417,400,000 | ||
| State | |||
| Income Tax [Line Items] | |||
| Operating loss carryforwards | 61,700,000 | ||
| Tax Benefit For Issuance of Shares to Noncontrolling Interest | |||
| Income Tax [Line Items] | |||
| Valuation allowance | $ 2,000,000 | ||
| Conversion of common shares from Class C to Class A | Common Class A | |||
| Income Tax [Line Items] | |||
| Income tax benefit | $ 0 | $ 7,200,000 | $ 20,000,000 |