Shareholders' equity (Details) (USD $)
|
3 Months Ended | 6 Months Ended | |||
---|---|---|---|---|---|
Jun. 30, 2011
|
Mar. 31, 2011
|
Jun. 30, 2010
|
Jun. 30, 2010
|
Dec. 31, 2010
|
|
Disclosure Shareholders Equity Details | |||||
Dividends declared per Common Share | $ 0.35 | $ 0.33 | $ 0.33 | $ 0.64 | |
Common Shares in treasury - shares | 4,862,746 | 6,151,707 |