Shareholders' Equity Common Stock (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2020	Dec. 31, 2018	Dec. 31, 2019
Class of Stock
Common Stock, Voting Rights		1
Common Stock, Shares Authorized		500,000,000		500,000,000
Common Stock, Shares, Issued		304,122,180		303,652,553
stock acquired during period value employee stock ownership plan	$ 34.0	$ 50.0	$ 50.0
Common Class B [Member]
Class of Stock
Common Stock, Voting Rights		0.1
Common Stock, Shares Authorized		100,000,000		100,000,000
Common Stock, Shares, Issued		0		0
Common Stock, shares outstanding		0		0
Common Stock [Member]
Class of Stock
Common Stock, Shares Authorized		500,000,000
stock acquired during period shares employee stock ownership plan	2,200,000	3,337,000	2,383,625