Equity (Common Stock Changes in Number of Shares Issued, Held in Treasury and Outstanding) (Details) - shares |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Increase (Decrease) in Stockholders' Equity [Roll Forward] | |||
| Beginning Balance | 660,111,339 | ||
| Ending Balance | 660,111,339 | 660,111,339 | |
| Issued | |||
| Increase (Decrease) in Stockholders' Equity [Roll Forward] | |||
| Beginning Balance | 660,100,000 | 660,100,000 | 660,100,000 |
| Common Stock issued | 0 | 0 | 0 |
| Common Stock acquired | 0 | 0 | 0 |
| Stock-based compensation programs | 0 | 0 | 0 |
| Ending Balance | 660,100,000 | 660,100,000 | 660,100,000 |
| Held In Treasury | |||
| Increase (Decrease) in Stockholders' Equity [Roll Forward] | |||
| Beginning Balance | 230,500,000 | 213,000,000 | 205,300,000 |
| Common Stock issued | 0 | 0 | 0 |
| Common Stock acquired | (11,500,000) | (25,100,000) | (12,100,000) |
| Stock-based compensation programs | (4,500,000) | (7,600,000) | (4,400,000) |
| Ending Balance | 237,500,000 | 230,500,000 | 213,000,000 |
| Outstanding | |||
| Increase (Decrease) in Stockholders' Equity [Roll Forward] | |||
| Beginning Balance | 429,600,000 | 447,100,000 | 454,800,000 |
| Common Stock issued | 0 | 0 | 0 |
| Common Stock acquired | (11,500,000) | (25,100,000) | (12,100,000) |
| Stock-based compensation programs | (4,500,000) | (7,600,000) | (4,400,000) |
| Ending Balance | 422,600,000 | 429,600,000 | 447,100,000 |