Revenue - Contract Balances (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Contract assets	$ 1,383.7		$ 1,295.0
Contract liabilities	4,252.2		4,085.1
Net contract assets (liabilities)	(2,868.5)		$ (2,790.1)
Contract assets, increase (decrease)	88.7
Contract (liabilities), (increase) decrease	(167.1)
Net contract assets (liabilities), increase (decrease)	$ (78.4)
Contract assets, increase (decrease), percent	6.80%
Contract (liabilities), (increase) decrease, percent	(4.10%)
Net contract assets (liabilities), increase (decrease), percent	(2.80%)
Contract with Customer, Liability, Revenue Recognized	$ 867.2	$ 836.3
Performance obligation satisfied in previous periods	$ 167.7