Fair Value Measures - Carrying Amount and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Carrying Value
Financial Assets:
Cash and cash equivalents	$ 18,990	$ 11,475
FHLB and FRB stock	1,565	1,392
Loans and leases held for investment, net	73,284	83,627
Financial Liabilities:
Deposits	79,032	81,526
Borrowed funds	28,892	21,267
Estimated Fair Value
Financial Assets:
Cash and cash equivalents	18,990	11,475
FHLB and FRB stock	1,565	1,392
Loans and leases held for investment, net	68,431	79,333
Financial Liabilities:
Deposits	78,660	81,247
Borrowed funds	28,770	21,082
Estimated Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial Assets:
Cash and cash equivalents	18,990	11,475
FHLB and FRB stock	0	0
Loans and leases held for investment, net	0	0
Financial Liabilities:
Deposits	50,252	59,972
Borrowed funds		0
Estimated Fair Value | Significant Other Observable Inputs (Level 2)
Financial Assets:
Cash and cash equivalents		0
FHLB and FRB stock	1,565	1,392
Loans and leases held for investment, net		0
Financial Liabilities:
Deposits	28,408	21,275
Borrowed funds	28,770	21,082
Estimated Fair Value | Significant Unobservable Inputs (Level 3)
Financial Assets:
Cash and cash equivalents		0
FHLB and FRB stock		0
Loans and leases held for investment, net	68,431	79,333
Financial Liabilities:
Deposits		0
Borrowed funds		$ 0