Financial Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Debt Instrument [Line Items]
Additional long-term investments, no market prices	$ 37	$ 39
Gross unrealized gains on fiduciary assets during period	1	7
Gross unrealized losses (pre-tax) on fiduciary assets during period	6	10	7
Senior Debt Obligations Due 2014 [Member]
Debt Instrument [Line Items]
Senior Notes due 2014, adjusted by the fair value of interest rate swap	$ 250