Debt - Borrowings and Repayments (Detail) - USD ($) $ in Millions	1 Months Ended		3 Months Ended		6 Months Ended
	May 31, 2022	Feb. 28, 2022	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Debt
New borrowings					$ 5,360	$ 1,707
Debt repayments					4,683	2,326
Premiums paid on early extinguishment of debt						211
Loss on early extinguishment of debt				$ (220)		(220)
Unamortized discounts and debt issuance costs			$ 85		85		$ 80
Low income housing investments [Member]
Debt
Interest expense			$ 4	$ 3	6	$ 5
Commercial Paper Program [Member]
Debt
Commercial paper repayments					4,100
Commercial paper borrowings					$ 3,400
Term Loan [Member]
Debt
Interest rate (as a percent)			2.30%		2.30%
New borrowings	$ 1,000
4.15% senior notes due 2032 [Member]
Debt
Debt instrument face amount	$ 1
Interest rate (as a percent)	4.15%
New borrowings	$ 992
2.90% senior notes due 2022 [Member]
Debt
Interest rate (as a percent)	2.90%
Debt repayments	$ 500
2.40% senior notes due 2023 [Member]
Debt
Interest rate (as a percent)			2.40%		2.40%
Financing leases and other [Member]
Debt
Debt repayments					$ 42
Financing leases and other [Member] | Low income housing investments [Member]
Debt
Note issued		$ 183			$ 183