Income Taxes (Narrative) (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended	9 Months Ended		12 Months Ended
	Apr. 17, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Line Items]
Unrecognized tax benefits		$ 199.9			$ 199.9	$ 199.9			$ 146.4
Increase in unrecognized tax benefits resulting from current period tax positions						22.8
Increase in unrecognized tax benefits resulting from prior period tax positions						86.9
Decrease in unrecognized tax benefits resulting from prior period tax positions						40.4
Decrease in unrecognized tax benefits resulting from settlement agreement	$ 43.1					13.4
U.S. federal statutory tax rate (percent)				35.00%	21.00%
Net expense in consolidated income statements related to change in tax law						239.0
Expense related to repatriation tax and future repatriation effect on foreign investments						453.0
Expense related to repatriation tax and future repatriation effect on foreign investments impacting income tax provision						420.5
Impact of new tax law on equity affiliate expense						32.5
Change In tax rate, deferred tax liability, income tax (expense) benefit						214.0
Component of tax-related adjustment payable over eight years						364.1
Component of tax-related adjustment resulting from withholding taxes and other impacts						56.4
Foreign tax credits expected to offset repatriation tax		71.5			$ 71.5	71.5
Tax liabilities not expected to be offset by foreign tax credits		292.6			292.6	292.6
Transition tax for accumulated foreign earnings, liability, noncurrent		234.8			$ 234.8	$ 234.8
Effective tax rate (percent)						30.60%
Deferred foreign income tax expense (benefit)			$ 38.8
Income tax payments, net of refunds						$ 319.1	$ 1,109.8
Discontinued Operations
Income Tax Disclosure [Line Items]
Tax adjustments, settlements, and unusual provisions		25.8
Continuing Operations
Income Tax Disclosure [Line Items]
Tax adjustments, settlements, and unusual provisions		$ 9.1
Forecast
Income Tax Disclosure [Line Items]
U.S. federal statutory tax rate (percent)								24.50%