Shareholders' equity (Rollforward Of Changes In Common Stock Shares Issued And Outstanding) (Details)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Changes In Common Stock Shares Issues And Outstanding [Roll Forward]
Shares issued, beginning of year	342,832,412	342,832,412	341,094,559
Exercise of stock options	0	0	1,737,853
Shares issued, end of year	342,832,412	342,832,412	342,832,412
Common Shares in treasury, end of year	(3,038,477)	(2,510,878)	(5,905,136)
Shares issued and outstanding, end of year	339,793,935	340,321,534	336,927,276
Balance, beginning of year	(9,467)	(9,467)	(101,481)
Shares redeemed	0	0	92,014
Balance, end of year	(9,467)	(9,467)	(9,467)