Short-Term Debt - Schedule of Company's Aggregate Credit Facility Commitments, Letter of Credit Sub-Limit Under Revolving Credit Facility and Commercial Paper Limit and Available Capacity (Details) - USD ($) $ in Millions |
Dec. 31, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Revolving Credit Facility | ||
| Short-term Debt [Line Items] | ||
| Credit Facility Commitment | $ 2,250 | $ 2,262 |
| Available Credit Facility/Credit Capacity | 2,174 | 2,177 |
| Revolving Credit Facility | Letter of Credit | ||
| Short-term Debt [Line Items] | ||
| Credit Facility Commitment | 150 | 150 |
| Available Credit Facility/Credit Capacity | 74 | 69 |
| Commercial Paper Program | ||
| Short-term Debt [Line Items] | ||
| Commercial Paper Limit | 2,100 | 2,100 |
| Available Commercial Paper Capacity | $ 1,314 | $ 1,146 |