Shareholders' Equity (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Equity, Class of Treasury Stock [Line Items]
Ordinary shares authorized (in shares)	1,000,000,000	1,000,000,000
Subscriber ordinary shares authorized (in shares)	2
Distributable reserves	$ 9,500
Treasury Stock
Consideration paid for treasury stock purchased	205.8	151.8	1.7
Share Buy-back Program
Authorized amount of share buy-back program	500
Cost of share repurchases		151.8
Income Access Share Arrangements
Cash dividends paid to Income Access Share Trustee	81.5	67.6	58.3
Ordinary Shares
Equity, Class of Treasury Stock [Line Items]
Treasury stock acquired (in shares)	4,500,000	2,700,000	20,000
Share Buy-back Program
Number of shares repurchased	3,631,571
Cost of share repurchases	$ 106.5
Authorized number of shares under share buy-back program	56,253,208
Ordinary Shares | Shares held by EBT
Treasury Stock
Treasury stock held (in shares)	3,800,000	4,600,000	4,400,000
Ordinary Shares | Shares held under share buy-back program
Treasury Stock
Treasury stock held (in shares)	2,700,000	0	0
ADS
Equity, Class of Treasury Stock [Line Items]
Treasury stock acquired (in shares)	900,000	800,000	20,000
ADS | Shares held by EBT
Treasury Stock
Treasury stock held (in shares)	1,100,000	2,400,000	3,200,000
ADS | Shares held under share buy-back program
Treasury Stock
Treasury stock held (in shares)	300,000	0	0