Commitments and Contingencies (Future Minimum Operating Lease Payments) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating leases, rent expense, minimum rentals	$ 175	$ 122	$ 129
Real Estate Leases [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2013	102
2014	85
2015	72
2016	58
2017	40
Thereafter	82
Total	439
Non-Rental Equipment Leases [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2013	29
2014	22
2015	19
2016	15
2017	14
Thereafter	16
Total	$ 115