Shareholders' Equity (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
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
Cash dividends paid to Income Access Share Trustee	67.6	58.3	45.9
ESOT
Equity, Class of Treasury Stock [Line Items]
Consideration paid for treasury stock purchased	$ 151.8	$ 1.7	$ 1.0
ESOT | Ordinary Shares
Equity, Class of Treasury Stock [Line Items]
Treasury stock held (in shares)	4,600,000	4,400,000	5,800,000
Treasury stock acquired (in shares)	2,700,000	20,000	100,000
ESOT | ADS
Equity, Class of Treasury Stock [Line Items]
Treasury stock held (in shares)	2,400,000	3,200,000	4,000,000
Treasury stock acquired (in shares)	800,000	20,000	20,000