Long-term Commitments (Operating Lease Agreements) (Details) $ in Millions	Dec. 31, 2015 USD ($)
Gross Rental Commitments
2016, Gross Rental Commitments	$ 372
2017, Gross Rental Commitments	341
2018, Gross Rental Commitments	311
2019, Gross Rental Commitments	259
2020, Gross Rental Commitments	224
Subsequent years, Gross Rental Commitments	847
Rental from Subleases
2016, Rentals from Subleases	47
2017, Rentals from Subleases	44
2018, Rentals from Subleases	42
2019, Rentals from Subleases	35
2020, Rentals from Subleases	32
Subsequent years, Rentals from Subleases	5
Net Rental Commitments
2016, Net Rental Commitments	325
2017, Net Rental Commitments	297
2018, Net Rental Commitments	269
2019, Net Rental Commitments	224
2020, Net Rental Commitments	192
Subsequent years, Net Rental Commitments	$ 842

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Operating Leases Future Minimum Payments Due, Net of Sublease Receivable [Abstract]

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