Derivative Financial Instruments - Balance Sheet Offsetting, Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Derivative Liabilities
Gross Amounts of Recognized Liabilities	$ 274	$ 237
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	274	237
Financial Instruments (Collateral)	(117)	(85)
Cash Collateral Pledged	(81)	(71)
Net Amount	76	81
Repurchase, securities lending, and similar arrangements
Securities Sold under Agreements to Repurchase, Gross	97	0
Securities Sold under Agreements to Repurchase, Asset	0	0
Securities Sold under Agreements to Repurchase	97	0
Financial Instruments (Collateral)	0	0
Cash Collateral Pledged	0	0
Net Amount	97	0
Total
Gross Amounts of Recognized Liabilities	371	237
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	371	237
Financial Instruments (Collateral)	(117)	(85)
Cash Collateral Pledged	(81)	(71)
Net Amount	173	81
Interest rate swaps
Derivative Liabilities
Gross Amounts of Recognized Liabilities	0	0
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	0	0
Derivative Liability, Not Offset, Policy Election Deduction	0	0
Cash Collateral Pledged	0	0
Net Amount	0	0
Foreign exchange forwards and swaps
Derivative Liabilities
Gross Amounts of Recognized Liabilities	156	208
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	156	208
Derivative Liability, Not Offset, Policy Election Deduction	(66)	(84)
Cash Collateral Pledged	(14)	(45)
Net Amount	76	79
Client foreign currency options
Derivative Liabilities
Gross Amounts of Recognized Liabilities	2	2
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	2	2
Derivative Liability, Not Offset, Policy Election Deduction	(1)	(1)
Cash Collateral Pledged	(1)	0
Net Amount	0	1
Client interest rate derivatives
Derivative Liabilities
Gross Amounts of Recognized Liabilities	116	27
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	116	27
Derivative Liability, Not Offset, Policy Election Deduction	(50)	0
Cash Collateral Pledged	(66)	(26)
Net Amount	$ 0	$ 1