Summary of Significant Accounting Policies - Government and Commercial Receivables (Details) |
6 Months Ended |
|---|---|
Jun. 30, 2018 | |
| Accounting Policies [Abstract] | |
| Financing receivable, past due period | 90 days |
| X | ||||||||||
- Definition Threshold period past due for delinquent or nonaccrual of financing receivable. No definition available.
|
| X | ||||||||||
- References No definition available.
|