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Income Taxes Schedule of Unrecognized Tax Benefits Activity (Tables) | 12 Months Ended
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Dec. 31, 2017
Income Tax Disclosure [Abstract] |
Schedule of Unrecognized Tax Benefits Activity [Table Text Block] | The table below summarizes the activity related to our unrecognized tax benefits.
| Years ended December 31,
| 2017 |  | 2016 |  | 2015
Balance at beginning of period | $ | 246.7 |  |  | $ | 226.9 |  |  | $ | 238.0 |
Increases as a result of tax positions taken during a prior year | 6.3 |  |  | 65.0 |  |  | 5.2 |
Decreases as a result of tax positions taken during a prior year | (8.1 | ) |  | (47.5 | ) |  | (19.7 | )
Settlements with taxing authorities | (0.8 | ) |  | (4.6 | ) |  | (4.1 | )
Lapse of statutes of limitation | (3.3 | ) |  | (11.8 | ) |  | (3.8 | )
Increases as a result of tax positions taken during the current year | 31.1 |  |  | 18.7 |  |  | 11.3 |
Balance at end of period | $ | 271.9 |  |  | $ | 246.7 |  |  | $ | 226.9 |

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