Consolidated Balance Sheets Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounts Receivable, Allowance for Credit Loss	$ 12.6	$ 19.9
Preferred Stock, Shares Authorized	1.5	1.5
Preferred Stock, Shares Unissued	1.5	1.5
Common Stock, Shares Authorized	400.0	400.0
Restricted Cash and Cash Equivalents	$ 111.4	$ 171.6
Property, Plant and Equipment, Gross	9,272.5	8,253.4
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	2,161.9	1,919.0
Partially-Owned Subsidiaries [Member]
Property, Plant and Equipment, Gross	2,065.3	2,032.0
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	$ 527.7	$ 472.0
Common Stock [Member]
Common Stock, Shares, Issued	119.7	133.3