Significant Accounting Policies - Concentrations of Credit Risk (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Accounting Policies [Abstract] | |||
| Minimum period after receivable balances are past due that significant accounts are reviewed individually for collectability (greater than) | 90 days | ||
| Bad debt expense | $ 3.0 | $ 3.3 | $ 0.6 |