Retirement Plans - Weighted Average Assumptions Used to Determine Benefit Obligation (Details) |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Pension Plan | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Discount rate | 4.20% | 0.70% |
| Other Postretirement Benefit Plan | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Discount rate | 3.60% |