Commitmets and Contingencies (Future Minimum Lease Commitments) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	$ 1,880
Operating Leases, Future Minimum Payments, Due in Two Years	1,863
Operating Leases, Future Minimum Payments, Due in Three Years	1,668
Operating Leases, Future Minimum Payments, Due in Four Years	1,542
Operating Leases, Future Minimum Payments, Due in Five Years	1,437
Operating Leases, Future Minimum Payments, Due Thereafter	7,276
Operating Leases, Future Minimum Payments Due	$ 15,666