Equity (Common Stock Changes in Number of Shares Issued, Held in Treasury and Outstanding) (Details)		3 Months Ended
	Aug. 02, 2019 USD ($) shares	Mar. 31, 2020 shares	Mar. 31, 2019 shares	Sep. 30, 2009 USD ($)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning		666,305,189
Balance, ending		666,305,189
Exchangeable surplus notes (in shares)		0.0	6,100,000
Issued
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning		666,300,000
Common Stock issued		0.0
Common Stock acquired		0.0
Stock-based compensation programs		0.0
Balance, ending		666,300,000
Held In Treasury
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning		267,500,000
Common Stock issued		0.0
Common Stock acquired		6,700,000
Stock-based compensation programs		(1,700,000)
Balance, ending		272,500,000
Outstanding
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning		398,800,000
Common Stock issued		0.0
Common Stock acquired		(6,700,000)
Stock-based compensation programs		1,700,000
Balance, ending		393,800,000
Long-term Debt | Exhangeable Surplus Notes
Class of Stock [Line Items]
Debt Instrument, Face Amount | $				$ 500,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exchangeable surplus notes (in shares)	6,200,000
Debt Instrument, Convertible, Conversion Ratio	12.3877
Surplus notes principal amount, for each | $	$ 1,000