Stockholders' Equity - Changes in Accumulated Other Comprehensive Income by Component (Parenthetical) (Details) $ in Millions |
6 Months Ended |
|---|---|
|
Jun. 30, 2017
USD ($)
| |
| Equity [Abstract] | |
| Net amount of settlement gains (losses) on derivative instruments included in accumulated OCI to be amortized over next 12 months, before tax | $ (5.7) |
| Net amount of settlement gains (losses) on derivative instruments included in accumulated OCI to be amortized over next 12 months, after tax | $ (3.5) |