Commitments And Contingencies (Narrative) (Details) $ in Millions	Dec. 31, 2017 USD ($)
Loss Contingencies [Line Items]
Liability for Uncertainty in Income Taxes, Noncurrent	$ 98
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	140
Business Combination, Contingent Consideration, Liability	122
Unrecorded Unconditional Purchase Obligation Payable in Common Stock Per Year | Maximum
Loss Contingencies [Line Items]
Unrecorded Unconditional Purchase Obligation	10
Unrecorded Unconditional Purchase Obligation Payable in Common Stock | Maximum
Loss Contingencies [Line Items]
Unrecorded Unconditional Purchase Obligation	32
Transitional impacts of the U.S. Tax Cuts and Jobs Act [Member]
Loss Contingencies [Line Items]
Accrued Income Taxes, Noncurrent	96
Accrued Income Taxes	104
Accrued Income Taxes, Current	$ 8