Condensed Balance Sheets Parenthetical - USD ($) shares in Millions, $ in Millions |
Sep. 30, 2016 |
Dec. 31, 2015 |
Sep. 30, 2015 |
|---|---|---|---|
| ASSETS | |||
| Accumulated depreciation | $ 1,788.6 | $ 1,499.4 | $ 1,411.9 |
| Shareholders' equity: | |||
| Common stock, par value | $ 1.00 | $ 1.00 | $ 1.00 |
| Common stock, authorized (in shares) | 240.0 | 240.0 | 120.0 |
| Common stock, issued | 165.3 | 165.1 | 77.6 |
| Common stock, outstanding | 165.3 | 165.1 | 77.6 |