Share-Based Compensation (Changes In Share Options Awards) (Details) (GBP £) In Millions, except Per Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Options [Member]
Outstanding at the beginning of the period	2.6	4.5
Forfeited during the period	0	(0.1)
Exercised during the year	(1.0)	(1.3)
Outstanding at the end of the period	1.6	3.1
Exercisable at the end of the period	1.6	3.1
Weighted Average Exercise Price (Sterling) [Member]
Outstanding at the beginning of the period Weighted Average Exercise Price	£ 7.31	£ 7.85
Forfeited during the period Weighted Average Exercise Price	£ 0.00	£ 14.80
Exercised during the period Weighted Average Exercise Price	£ 7.38	£ 8.29
Outstanding at the end of the period Weighted Average Exercise Price	£ 7.26	£ 7.33
Exercisable at the end of the period Weighted Average Exercise Price	£ 7.26	£ 7.33