Basis of Presentation and Principles of Consolidation (Narrative) (Details) $ / shares in Units, $ in Millions	Mar. 04, 2021	Mar. 31, 2021 USD ($) $ / shares	Dec. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Stock split conversion ratio	2
Common Stock, Par or Stated Value Per Share | $ / shares		$ 0.001
Total equity		$ 5,521.7	$ 5,451.9	$ 4,445.7	$ 4,596.2
Common Stock
Total equity		0.6	0.6	0.6	0.6
Common Stock | Stock Split [Member]
Total equity		0.3	0.3	0.3	0.3
Additional Paid in Capital
Total equity		2,105.7	2,068.1	1,720.3	1,683.0
Additional Paid in Capital | Stock Split [Member]
Total equity		$ (0.3)	$ (0.3)	$ (0.3)	$ (0.3)