Income Taxes (Unrecognized Tax Benefit Rollforward) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Tax Disclosure [Abstract]
Additions based on current year tax positions	$ 4	$ 1
Additions based on prior year tax positions	4	13
Reductions for prior year tax positions	(1)	(21)
Reductions for settlements	(2)	(38)
Reductions for lapse of statute of limitations	(8)	(11)
Unrecognized tax benefit	$ 225	$ 228	$ 284