Shareholders' equity (Rollforward Of Changes In Common Stock Shares Issued And Outstanding) (Details) - shares			12 Months Ended
	Aug. 04, 2022	Jan. 17, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Shares issued, Beginning of year			474,021,114	477,605,264	479,783,864
Treasury Stock, Shares, Retired	(13,179,100)	(14,465,400)	(27,644,500)	(3,584,150)	(2,178,600)
Shares issued, End of year			446,376,614	474,021,114	477,605,264
Common Shares in treasury, end of year			(31,781,758)	(47,448,502)	(26,872,639)	(27,812,297)
Stock Issued During Period, Shares, New Issues			2,947,272	3,484,487	2,345,208
Treasury Stock, Shares, Acquired			(14,925,028)	(27,644,500)	(3,584,150)
Shares issued and outstanding, end of year			414,594,856	426,572,612	450,732,625