Revenue Recognition (Balance Sheet Impact Upon Adoption) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Oct. 01, 2018	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Assets
Cash and cash items	$ 2,923.3	$ 2,791.3	$ 2,791.3
Short-term investments	12.3	184.7	184.7
Trade receivables, net	1,268.2	1,207.2	1,207.2
Inventories	403.4	396.1	396.1
Contracts in progress, less progress billings		0.0	77.5
Prepaid expenses	74.9	129.6	129.6
Other receivables and current assets		399.5	295.8
Total Current Assets	5,089.9	5,108.4	5,082.2
Total Noncurrent Assets	14,052.1	14,096.1	14,096.1
Total Assets	19,142.0	19,204.5	19,178.3
Liabilities and Equity
Payables and accrued liabilities	1,738.3	1,844.0	1,817.8
Accrued income taxes	111.9	59.6	59.6
Short-term borrowings	23.0	54.3	54.3
Current portion of long-term debt	430.3	406.6	406.6
Total Current Liabilities	2,303.5	2,364.5	2,338.3
Total Noncurrent Liabilities	5,635.1	5,663.7	5,663.7
Total Liabilities	7,938.6	8,028.2	8,002.0
Total Equity	11,203.4	11,176.3	11,176.3	$ 10,321.2	$ 10,185.5
Total Liabilities and Equity	$ 19,142.0	19,204.5	$ 19,178.3
ASU Update 2014-09 | New Revenue Standard Adjustments
Assets
Cash and cash items		0.0
Short-term investments		0.0
Trade receivables, net		0.0
Inventories		0.0
Contracts in progress, less progress billings		(77.5)
Prepaid expenses		0.0
Other receivables and current assets		103.7
Total Current Assets		26.2
Total Noncurrent Assets		0.0
Total Assets		26.2
Liabilities and Equity
Payables and accrued liabilities		26.2
Accrued income taxes		0.0
Short-term borrowings		0.0
Current portion of long-term debt		0.0
Total Current Liabilities		26.2
Total Noncurrent Liabilities		0.0
Total Liabilities		26.2
Total Equity		0.0
Total Liabilities and Equity		$ 26.2