Commitments and Contingencies (Commitments) (Details) $ in Millions	Dec. 31, 2015 USD ($)
Other Commitments [Line Items]
Operating Leases - 2016	$ 2,379
Operating Leases - 2017	2,235
Operating Leases - 2018	2,046
Operating Leases - 2019	1,900
Operating Leases - 2020	1,679
Operating Leases - Thereafter	5,583
Operating Leases - Total	15,822
Purchase Obligation - 2016	2,865
Purchase Obligation - 2017	3,150
Purchase Obligation - 2018	772
Purchase Obligation - 2019	714
Purchase Obligation - 2020	629
Purchase Obligation - Thereafter	1,304
Purchase Obligation - Total	$ 9,434