Fair Value - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	$ 9,295	$ 9,203
Marketable equity securities	100	98
Fair value of derivative financial instruments	110	0
Fair value of derivative financial instruments	204	0
Fair Value, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	9,295	9,203
Marketable equity securities	100	98
Loans held for sale	65	99
Fair value of derivative financial instruments	110
Fair value of derivative financial instruments	204
Fair Value, Recurring | Interest rate contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of derivative financial instruments	106
Fair value of derivative financial instruments	199
Fair Value, Recurring | Other derivative
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of derivative financial instruments	4
Fair value of derivative financial instruments	5
Fair Value, Recurring | Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Marketable equity securities	33	34
Loans held for sale	0	0
Fair value of derivative financial instruments	0
Fair value of derivative financial instruments	0
Fair Value, Recurring | Level 1 | Interest rate contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of derivative financial instruments	0
Fair value of derivative financial instruments	0
Fair Value, Recurring | Level 1 | Other derivative
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of derivative financial instruments	0
Fair value of derivative financial instruments	0
Fair Value, Recurring | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	9,109	8,996
Marketable equity securities	67	64
Loans held for sale	65	99
Fair value of derivative financial instruments	109
Fair value of derivative financial instruments	203
Fair Value, Recurring | Level 2 | Interest rate contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of derivative financial instruments	105
Fair value of derivative financial instruments	199
Fair Value, Recurring | Level 2 | Other derivative
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of derivative financial instruments	4
Fair value of derivative financial instruments	4
Fair Value, Recurring | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	186	207
Marketable equity securities	0	0
Loans held for sale	0	0
Fair value of derivative financial instruments	1
Fair value of derivative financial instruments	1
Fair Value, Recurring | Level 3 | Interest rate contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of derivative financial instruments	1
Fair value of derivative financial instruments	0
Fair Value, Recurring | Level 3 | Other derivative
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of derivative financial instruments	0
Fair value of derivative financial instruments	1
Fair Value, Recurring | U.S. Treasury
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	1,931	2,005
Fair Value, Recurring | U.S. Treasury | Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | U.S. Treasury | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	1,931	2,005
Fair Value, Recurring | U.S. Treasury | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Government agency
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	206	221
Fair Value, Recurring | Government agency | Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Government agency | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	206	221
Fair Value, Recurring | Government agency | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Residential mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	5,052	4,729
Fair Value, Recurring | Residential mortgage-backed securities | Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Residential mortgage-backed securities | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	5,052	4,729
Fair Value, Recurring | Residential mortgage-backed securities | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Commercial mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	1,520	1,640
Fair Value, Recurring | Commercial mortgage-backed securities | Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Commercial mortgage-backed securities | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	1,520	1,640
Fair Value, Recurring | Commercial mortgage-backed securities | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Corporate bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	586	608
Fair Value, Recurring | Corporate bonds | Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Corporate bonds | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	400	401
Fair Value, Recurring | Corporate bonds | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	$ 186	$ 207