Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning of year	$ 36,834.0
Total other comprehensive income	9.0	$ 19.0
End of year	33,842.0
Foreign Currency
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning of year	(127.0)	(165.0)
Other comprehensive income before reclassifications	8.0	18.0
Amounts reclassified from accumulated other comprehensive income	0.0	0.0
Total other comprehensive income	8.0	18.0
End of year	(119.0)	(147.0)
Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning of year	(5.0)	(7.0)
Other comprehensive income before reclassifications	0.0	0.0
Amounts reclassified from accumulated other comprehensive income	1.0	1.0
Total other comprehensive income	1.0	1.0
End of year	(4.0)	(6.0)
Pension and Other Postretirement Benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning of year	(173.0)	(186.0)
Other comprehensive income before reclassifications	0.0	0.0
Amounts reclassified from accumulated other comprehensive income	0.0	0.0
End of year	(173.0)	(186.0)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning of year	(305.0)	(358.0)
Other comprehensive income before reclassifications	8.0	18.0
Amounts reclassified from accumulated other comprehensive income	1.0	1.0
Total other comprehensive income	9.0	19.0
End of year	$ (296.0)	$ (339.0)