Long-Term Debt - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Long-term Debt
Repayments of near-term maturities of debt	$ 4,300	$ 0	$ 174
Repayments of floating interest rate notes	1,100
Senior Notes
Long-term Debt
Repayments of near-term maturities of debt	224
Estimate of Fair Value | Level 1
Long-term Debt
Fair value of long-term debt	33,000			$ 33,800
Third Quarter Repayments | Senior Notes
Long-term Debt
Cash tender	$ 3,000