Share-based Compensation Plans (by Share-based Payment Award) (Details)	12 Months Ended
	Dec. 31, 2011
SARs and Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award outstanding (in shares)	23,398,448
Performance Share Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award outstanding (in shares)	5,709,744
Portfolio Share Plan - Part A | SARs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award outstanding (in shares)	21,600,470
Award expiration period	5 - 7 years
Award vesting period	3 years cliff or graded vesting, subject to market or performance criteria for Executive Directors only
Sharesave Scheme | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award outstanding (in shares)	328,746
Award expiration period	6 months after vesting
Award vesting period	3 or 5 years
Exercise price of common stock, percent	80.00%
Stock Purchase Plan | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award outstanding (in shares)	793,706
Award expiration period	On vesting date
Award vesting period	1 to 5 years
Exercise price of common stock, percent	85.00%
Legacy Plans | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award outstanding (in shares)	675,526
Award expiration period	7 to 10 years
Award vesting period	3-10 years, subject to market or performance criteria
Portfolio Share Plan - Part B | Performance Share Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award outstanding (in shares)	5,709,744
Award expiration period	3Y
Award vesting period	3 years cliff or graded vesting, subject to market or performance criteria for Executive Directors only