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Business Combinations Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Jan. 05, 2018
Business Acquisition [Line Items]
Payments to acquire businesses, gross	$ 802.5
SIlver Spring Networks, Inc. [Member]
Business Acquisition [Line Items]
Purchase price, net of cash			$ 809.2
Cash acquired from acquisition		$ 97.8
Equity interest issued			$ 6.7