Fair Value Measurements (Aggregate Fair Value of Derivative Financial Instruments, Equity Securities and Debt (Details) $ in Millions	Jun. 30, 2019 USD ($)
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Assets:
Equity securities	$ 281
Derivative contracts	0
Total assets	281
Liabilities:
Debt	31,455
Derivative contracts	0
Total liabilities	31,455
Significant Other Observable Inputs (Level 2) [Member]
Assets:
Equity securities	0
Derivative contracts	377
Total assets	377
Liabilities:
Debt	169
Derivative contracts	663
Total liabilities	832
Significant Unobservable Inputs (Level 3) [Member]
Assets:
Equity securities	0
Derivative contracts	0
Total assets	0
Liabilities:
Debt	0
Derivative contracts	0
Total liabilities	0
Fair Value [Member]
Assets:
Equity securities	281
Derivative contracts	377
Total assets	658
Liabilities:
Debt	31,624
Derivative contracts	663
Total liabilities	$ 32,287