Debt Debt - Extinguishments of Debt (Details) $ in Millions	Jun. 30, 2019 USD ($)
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount	$ 1,100
Notes 3.700% due June 6, 2027 [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount	$ 675
Debt Instrument, Interest Rate, Stated Percentage	3.70%
Notes 5.000% due November 12, 2040 [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount	$ 175
Debt Instrument, Interest Rate, Stated Percentage	5.00%
Notes 4.875% due May 15, 2044 [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount	$ 75
Debt Instrument, Interest Rate, Stated Percentage	4.875%
Notes 4.685% due December 15, 2044 [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount	$ 175
Debt Instrument, Interest Rate, Stated Percentage	4.685%