Fair Value Measures - Financial Instruments Carried at Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Assets:
Total debt securities available for sale	$ 9,145	$ 9,060
Loans held-for-sale	902	1,115
Total debt securities available for sale
Assets:
Total debt securities available for sale	9,145	9,060
Mortgage-related Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	6,563	4,789
GSE certificates
Assets:
Total debt securities available for sale	1,221	1,297
GSE CMOs
Assets:
Total debt securities available for sale	5,162	3,301
Private Label CMOs
Assets:
Total debt securities available for sale	180	191
Other Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	2,582	4,271
U. S. Treasury obligations
Assets:
Total debt securities available for sale	198	1,487
GSE debentures
Assets:
Total debt securities available for sale	1,609	1,398
Asset-backed securities
Assets:
Total debt securities available for sale	302	361
Municipal bonds
Assets:
Total debt securities available for sale	6	30
Corporate bonds
Assets:
Total debt securities available for sale	343	885
Foreign notes
Assets:
Total debt securities available for sale	34	20
Capital trust notes
Assets:
Total debt securities available for sale	90	90
Recurring
Assets:
Fair Value	9,159	9,074
Mortgage servicing rights	1,111	1,033
Total assets at fair value	11,310	11,451
Liabilities:
Total liabilities at fair value	95	136
Recurring | Acquisition, development, and construction
Assets:
Loans held-for-sale	123
Recurring | Commercial and industrial
Assets:
Loans held-for-sale	9
Recurring | Mortgage Loans | Residential first mortgage loans
Assets:
Loans held-for-sale	770	1,115
Recurring | Interest rate swaps and swaptions
Assets:
Derivative assets	115	182
Liabilities:
Derivative liabilities	59	65
Recurring | Futures
Assets:
Derivative assets	0	2
Liabilities:
Derivative liabilities	1
Recurring | Rate lock commitments (fallout-adjusted)
Assets:
Derivative assets	12	9
Liabilities:
Derivative liabilities	3	10
Recurring | Mortgage-backed securities forwards
Assets:
Derivative assets	11	36
Liabilities:
Derivative liabilities	32	61
Recurring | Total debt securities available for sale
Assets:
Total debt securities available for sale	9,145	9,060
Recurring | Mortgage-related Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	6,563	4,789
Recurring | GSE certificates
Assets:
Total debt securities available for sale	1,221	1,297
Recurring | GSE CMOs
Assets:
Total debt securities available for sale	5,162	3,301
Recurring | Private Label CMOs
Assets:
Total debt securities available for sale	180	191
Recurring | Other Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	2,582	4,271
Recurring | U. S. Treasury obligations
Assets:
Total debt securities available for sale	198	1,487
Recurring | GSE debentures
Assets:
Total debt securities available for sale	1,609	1,398
Recurring | Asset-backed securities
Assets:
Total debt securities available for sale	302	361
Recurring | Municipal bonds
Assets:
Total debt securities available for sale	6	30
Recurring | Corporate bonds
Assets:
Total debt securities available for sale	343	885
Recurring | Foreign notes
Assets:
Total debt securities available for sale	34	20
Recurring | Capital trust notes
Assets:
Total debt securities available for sale	90	90
Recurring | Equity securities:
Assets:
Equity securities:	14	14
Recurring | Mutual funds
Assets:
Equity securities:	14	14
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Fair Value	198	1,487
Mortgage servicing rights	0	0
Total assets at fair value	198	1,487
Liabilities:
Total liabilities at fair value	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Acquisition, development, and construction
Assets:
Loans held-for-sale	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial and industrial
Assets:
Loans held-for-sale	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage Loans | Residential first mortgage loans
Assets:
Loans held-for-sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate swaps and swaptions
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Futures
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Rate lock commitments (fallout-adjusted)
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage-backed securities forwards
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Total debt securities available for sale
Assets:
Total debt securities available for sale	198	1,487
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage-related Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | GSE certificates
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | GSE CMOs
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Private Label CMOs
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	198	1,487
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U. S. Treasury obligations
Assets:
Total debt securities available for sale	198	1,487
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | GSE debentures
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Asset-backed securities
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal bonds
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign notes
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Capital trust notes
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities:
Assets:
Equity securities:	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mutual funds
Assets:
Equity securities:	0	0
Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Fair Value	8,929	7,587
Mortgage servicing rights	0	0
Total assets at fair value	9,957	8,922
Liabilities:
Total liabilities at fair value	92	126
Recurring | Significant Other Observable Inputs (Level 2) | Acquisition, development, and construction
Assets:
Loans held-for-sale	123
Recurring | Significant Other Observable Inputs (Level 2) | Commercial and industrial
Assets:
Loans held-for-sale	9
Recurring | Significant Other Observable Inputs (Level 2) | Mortgage Loans | Residential first mortgage loans
Assets:
Loans held-for-sale	770	1,115
Recurring | Significant Other Observable Inputs (Level 2) | Interest rate swaps and swaptions
Assets:
Derivative assets	115	182
Liabilities:
Derivative liabilities	59	65
Recurring | Significant Other Observable Inputs (Level 2) | Futures
Assets:
Derivative assets	0	2
Liabilities:
Derivative liabilities	1
Recurring | Significant Other Observable Inputs (Level 2) | Rate lock commitments (fallout-adjusted)
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0	0
Recurring | Significant Other Observable Inputs (Level 2) | Mortgage-backed securities forwards
Assets:
Derivative assets	11	36
Liabilities:
Derivative liabilities	32	61
Recurring | Significant Other Observable Inputs (Level 2) | Total debt securities available for sale
Assets:
Total debt securities available for sale	8,915	7,573
Recurring | Significant Other Observable Inputs (Level 2) | Mortgage-related Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	6,531	4,789
Recurring | Significant Other Observable Inputs (Level 2) | GSE certificates
Assets:
Total debt securities available for sale	1,221	1,297
Recurring | Significant Other Observable Inputs (Level 2) | GSE CMOs
Assets:
Total debt securities available for sale	5,162	3,301
Recurring | Significant Other Observable Inputs (Level 2) | Private Label CMOs
Assets:
Total debt securities available for sale	148	191
Recurring | Significant Other Observable Inputs (Level 2) | Other Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	2,384	2,784
Recurring | Significant Other Observable Inputs (Level 2) | U. S. Treasury obligations
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Other Observable Inputs (Level 2) | GSE debentures
Assets:
Total debt securities available for sale	1,609	1,398
Recurring | Significant Other Observable Inputs (Level 2) | Asset-backed securities
Assets:
Total debt securities available for sale	302	361
Recurring | Significant Other Observable Inputs (Level 2) | Municipal bonds
Assets:
Total debt securities available for sale	6	30
Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds
Assets:
Total debt securities available for sale	343	885
Recurring | Significant Other Observable Inputs (Level 2) | Foreign notes
Assets:
Total debt securities available for sale	34	20
Recurring | Significant Other Observable Inputs (Level 2) | Capital trust notes
Assets:
Total debt securities available for sale	90	90
Recurring | Significant Other Observable Inputs (Level 2) | Equity securities:
Assets:
Equity securities:	14	14
Recurring | Significant Other Observable Inputs (Level 2) | Mutual funds
Assets:
Equity securities:	14	14
Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Fair Value	32	0
Mortgage servicing rights	1,111	1,033
Total assets at fair value	1,155	1,042
Liabilities:
Total liabilities at fair value	3	10
Recurring | Significant Unobservable Inputs (Level 3) | Acquisition, development, and construction
Assets:
Loans held-for-sale	0
Recurring | Significant Unobservable Inputs (Level 3) | Commercial and industrial
Assets:
Loans held-for-sale	0
Recurring | Significant Unobservable Inputs (Level 3) | Mortgage Loans | Residential first mortgage loans
Assets:
Loans held-for-sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Interest rate swaps and swaptions
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Futures
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0
Recurring | Significant Unobservable Inputs (Level 3) | Rate lock commitments (fallout-adjusted)
Assets:
Derivative assets	12	9
Liabilities:
Derivative liabilities	3	10
Recurring | Significant Unobservable Inputs (Level 3) | Mortgage-backed securities forwards
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Total debt securities available for sale
Assets:
Total debt securities available for sale	32	0
Recurring | Significant Unobservable Inputs (Level 3) | Mortgage-related Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	32	0
Recurring | Significant Unobservable Inputs (Level 3) | GSE certificates
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | GSE CMOs
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Private Label CMOs
Assets:
Total debt securities available for sale	32	0
Recurring | Significant Unobservable Inputs (Level 3) | Other Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | U. S. Treasury obligations
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | GSE debentures
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Asset-backed securities
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Municipal bonds
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Corporate bonds
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Foreign notes
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Capital trust notes
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Equity securities:
Assets:
Equity securities:	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Mutual funds
Assets:
Equity securities:	$ 0	$ 0