Commitments and Contingencies (Leases) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Commitments and Contingencies Disclosure [Abstract]
Total rentals, net of sublease rentals	$ 850	$ 735	$ 591
Future total rentals on noncancellable operating leases	961
2013	287
2014	214
2015	146
2016	102
2017	48
Thereafter	$ 164