Derivative Financial Instruments (Notional Value Of Outstanding Cash Flow Hedge Contracts By Year Of Maturity And Net Unrealized (Loss) Gain Included In Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Foreign Exchange Forward [Member]
Derivative [Line Items]
Net unrealized gains (losses) included in accumulated other comprehensive income (loss), net of taxes	$ 33	$ (3)
Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Notional value of contracts outstanding	2,235	2,168
Designated as Hedging Instrument [Member] | Foreign Exchange Forward, Maturity 2019 [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Notional value of contracts outstanding	1,130	1,388
Designated as Hedging Instrument [Member] | Foreign Exchange Forward, Maturity 2020 [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Notional value of contracts outstanding	965	780
Designated as Hedging Instrument [Member] | Foreign Exchange Forward, Maturity 2021 [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Notional value of contracts outstanding	$ 140	$ 0