Fair Value Measurement - Assets Measured At Fair Value on Nonrecurring Basis (Details) - USD ($) $ in Thousands |
Dec. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Assets Held for Sale | $ 10,118 | $ 8,866 |
| Level 1 | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Assets Held for Sale | 0 | 0 |
| Level 2 | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Assets Held for Sale | 10,118 | 8,866 |
| Level 3 | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Assets Held for Sale | $ 0 | $ 0 |