Contingencies and Commitments (U.S. Repatriation Tax Commitments) (Details) $ in Millions	Dec. 31, 2017 USD ($) installment
Commitments and Contingencies Disclosure [Abstract]
U.S. repatriation tax commitments, number of annual installments | installment	8
U.S. repatriation tax commitments, 2018	$ 585
U.S. repatriation tax commitments, 2019	585
U.S. repatriation tax commitments, 2020	585
U.S. repatriation tax commitments, 2021	585
U.S. repatriation tax commitments, 2022	585
U.S. repatriation tax commitments, Thereafter	4,391
Total U.S. repatriation tax commitments	$ 7,316