Fair Value Measurements - MEC - Debt (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 49,762	$ 49,866
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	57,189	60,633
MEC
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	7,721	7,210
Long-term debt, fair value		$ 9,130
MEC | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 9,037