Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			0 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Jan. 02, 2012 Minimum [Member]	Jan. 02, 2012 Maximum [Member]
Summary of Significant Accounting Policies [Abstract]
Unbilled Audit Premiums	$ 1	$ 7	$ 23
Deposit contracts, liabilities	80	95
Depreciation	40	41	46
Intangible assets, net (excluding goodwill)	29	0
Interest payments	111	103	80
Income taxes paid	48	123	16
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
New accounting pronouncement or change in accounting principle, cumulative effect of change on equity				$ 50	$ 60