Pension and Savings Plans Changes in the Fair Value of Master Trust's Level 3 Investments (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Apr. 01, 2017	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Real estate interests
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period			$ 6.2
Assets Held At Reporting Date:
Fair value of plan assets at end of period			4.1	$ 6.2
Level 3
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period	$ 14.1	$ 13.8	6.2	11.8
Assets Held At Reporting Date:
Realized gains	0.6	0.0	(1.0)	2.6
Unrealized gains relatng to investments still held at the reporting date	(0.6)	2.2	1.4	(2.6)
Purchases, sales and settlements, net	(0.3)	(4.2)	(2.5)	(5.6)
Fair value of plan assets at end of period	$ 13.8	11.8	4.1	6.2
Level 3 | Real estate interests
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period			6.2
Assets Held At Reporting Date:
Fair value of plan assets at end of period			4.1	6.2
Pension Plans, Defined Benefit
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period			764.8	776.6
Assets Held At Reporting Date:
Fair value of plan assets at end of period		$ 776.6	$ 855.2	$ 764.8