Summary of Significant Accounting Policies (Effects of Adoption of Topic 606 - Unaudited Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Held for sale and other current assets	$ 3,135.3	$ 795.3
Other current liabilities	1,225.9	908.8
Other non-current liabilities	2,065.1	2,197.9
Retained earnings	10,929.6	$ 9,920.6
ASU 2014-09 | Before Adoption of Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Held for sale and other current assets	3,079.3
Other current liabilities	1,226.9
Other non-current liabilities	2,067.2
Retained earnings	$ 10,926.4