Share-Based Compensation (Movements On Share Awards) (Details) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 USD ($)	Dec. 31, 2014 GBP (£)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2014 Time Vested N y s e [Member]	Dec. 31, 2013 Time Vested N y s e [Member]	Dec. 31, 2012 Time Vested N y s e [Member]	Dec. 31, 2014 Time-Vested [Member]	Dec. 31, 2013 Time-Vested [Member]	Dec. 31, 2012 Time-Vested [Member]	Dec. 31, 2014 Performance Shares [Member]	Dec. 31, 2013 Performance Shares [Member]	Dec. 31, 2012 Performance Shares [Member]
Unvested at the beginning of year					13.9	16.5	17.3	0.1	0.3	0.6	0.4	0.3	0
Granted during the year					4.4	5.2	5.5				0.2	0.2	0.3
Forfeited during the year					(1.2)	(0.9)	(0.4)	0	0	0	0	0	0
Vested and distributed during the year					(5.6)	(6.9)	(5.9)	(0.1)	(0.2)	(0.3)	(0.1)	(0.1)	0
Unvested at the end of the year					11.5	13.9	16.5	0	0.1	0.3	0.5	0.4	0.3
Unvested at beginning of year Weighted Average Grant Date Fair Value	$ 25.00	£ 12.90
Granted during period Weighted Average Grant Date Fair Value	$ 34.35		$ 26.91	$ 24.84
Forfeited during the year Weighted Average Grant Date Fair Value	$ 24.43	£ 0.00
Vested and distributed during the period Weighted Average Grant Date Fair Value	$ 24.16	£ 12.90
Unvested at the end of the year Weighted Average Grant Date Fair Value	$ 29.00	£ 0.00	$ 25.00