Stockholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Equity, Class of Treasury Stock [Line Items]
Common shares repurchases			$ 3,306.0
Foreign currency translation reclassification adjustments	$ 16.7	$ 0.0	26.2	$ 4.7
Foreign currency translation reclassification adjustments, tax	12.7	(0.9)	17.1	14.7
Changes in benefit plans net gain/ (loss) and prior service (cost)/ credit reclassification adjustments impacting net income	0.6	0.4	0.6	1.4
Changes in income taxes associated with changes in benefit plans net gain/ (loss) and prior service (cost)/ credit	0.0	0.0	(0.6)	0.0
Reclassification adjustments impacting net income for unrealized gains (losses on available for sale securities	(0.2)	0.0	(0.2)	0.0
Change in income taxes associated with net unrealized gains on available for sale securities	(2.6)	$ (7.4)	(4.2)	$ (9.0)
Commercial Air [Member] | Discontinued Operations, Disposed of by Sale [Member]
Equity, Class of Treasury Stock [Line Items]
Reclassification adjustment from sale of the Commercial Air business	16.7
Accelerated Share Repurchase Program, Final Settlement in Third Quarter of 2017 [Member]
Equity, Class of Treasury Stock [Line Items]
Common shares repurchases			$ 512.0
Number of shares repurchased			9,250,000
Common Share Repurchases [Member]
Equity, Class of Treasury Stock [Line Items]
Common shares repurchases	$ 3,300.0
Equity Tender Offer [Member]
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased	57,300,000
Purchase price per share	$ 48
Open Market Repurchases [Member]
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased	818,071
Purchase price per share	$ 46.45