Operating Revenues - Contract Liabilities (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Contract liabilities		$ 1,000.0	$ 883.8
Overall change in contract liability balances		145.3
New deferred billings for current reporting period		916.4
Increase from acquisitions		0.7
Operating revenue recognized	$ (23.7)	773.3
Contract liabilities, revenue recognized related to prior years contracts		402.0
Contract With Customer, Liability, Net Other Activity		$ 1.5