Benefit Plans - Fair Value of pension plan assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Free Standing Derivative Liabilities | Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value		$ (2)
Free Standing Derivative Liabilities | Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value		(21)
Free Standing Derivative Liabilities | Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value		0
Pension benefits
Components of net periodic cost
Total plan assets at fair value	$ 2,520	$ 3,122
Total plan assets at fair value, allocation (as a percent)	100.00%	100.00%
Investments measured using the net asset value practical expedient	$ 4,109	$ 3,908
Securities lending obligation	(121)	(101)
Derivatives counterparty and cash collateral netting	(3)	(19)
Other net plan assets	20	77
Fair value of plan assets	6,525	6,987	$ 6,192
Pension benefits | Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	$ 506	$ 469
Total plan assets at fair value, allocation (as a percent)	20.10%	15.00%
Pension benefits | Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	$ 2,012	$ 2,651
Total plan assets at fair value, allocation (as a percent)	79.80%	84.90%
Pension benefits | Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	$ 2	$ 2
Total plan assets at fair value, allocation (as a percent)	0.10%	0.10%
Fair value of plan assets	$ 2	$ 2	0	$ 5
Pension benefits | Equity securities
Components of net periodic cost
Total plan assets at fair value	357	269
Pension benefits | Equity securities | Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	311	227
Pension benefits | Equity securities | Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	44	42
Pension benefits | Equity securities | Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	2	0
Fair value of plan assets	2	0
Pension benefits | Government bonds
Components of net periodic cost
Total plan assets at fair value	1,264	897
Pension benefits | Government bonds | Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	58	32
Pension benefits | Government bonds | Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	1,206	865
Pension benefits | Government bonds | Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	0	0
Pension benefits | Corporate
Components of net periodic cost
Total plan assets at fair value	696	1,711
Pension benefits | Corporate | Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	0	0
Pension benefits | Corporate | Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	696	1,709
Pension benefits | Corporate | Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	0	2
Fair value of plan assets	0	2	$ 0	$ 5
Pension benefits | Short-term investments
Components of net periodic cost
Total plan assets at fair value	200	245
Pension benefits | Short-term investments | Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	135	210
Pension benefits | Short-term investments | Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	65	35
Pension benefits | Short-term investments | Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	0	0
Pension benefits | Free Standing Derivative Assets
Components of net periodic cost
Total plan assets at fair value	4	21
Pension benefits | Free Standing Derivative Assets | Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	0	0
Pension benefits | Free Standing Derivative Assets | Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	4	21
Pension benefits | Free Standing Derivative Assets | Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	0	0
Pension benefits | Free Standing Derivative Liabilities
Components of net periodic cost
Total plan assets at fair value	(3)	(23)
Pension benefits | Free Standing Derivative Liabilities | Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	0
Pension benefits | Free Standing Derivative Liabilities | Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	(3)
Pension benefits | Free Standing Derivative Liabilities | Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	0
Pension benefits | Free Standing Derivative Other Assets
Components of net periodic cost
Total plan assets at fair value	2	2
Pension benefits | Free Standing Derivative Other Assets | Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	2	2
Pension benefits | Free Standing Derivative Other Assets | Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	0	0
Pension benefits | Free Standing Derivative Other Assets | Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	$ 0	$ 0