Fair Value Measures - Financial Instruments Carried at Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Assets:
Total debt securities available for sale	$ 8,723	$ 9,060
Total securities	8,736	9,074
Loans held-for-sale	1,325	1,115
Mortgage servicing rights	1,135	1,033
Acquisition, development, and construction
Assets:
Loans held-for-sale	168
Private Label CMOs
Assets:
Total debt securities available for sale	174
Total debt securities available for sale
Assets:
Total debt securities available for sale	8,723	9,060
Total mortgage-related debt securities
Assets:
Total debt securities available for sale	5,689	4,789
Total mortgage-related debt securities | GSE certificates
Assets:
Total debt securities available for sale	1,164	1,297
Total mortgage-related debt securities | GSE CMOs
Assets:
Total debt securities available for sale	4,351	3,301
Total mortgage-related debt securities | Private Label CMOs
Assets:
Total debt securities available for sale	174	191
Total other debt securities
Assets:
Total debt securities available for sale	3,034	4,271
Total other debt securities | U. S. Treasury obligations
Assets:
Total debt securities available for sale	195	1,487
Total other debt securities | GSE debentures
Assets:
Total debt securities available for sale	1,659	1,398
Total other debt securities | Asset-backed securities
Assets:
Total debt securities available for sale	313	361
Total other debt securities | Municipal bonds
Assets:
Total debt securities available for sale	6	30
Total other debt securities | Corporate bonds
Assets:
Total debt securities available for sale	737	885
Total other debt securities | Foreign notes
Assets:
Total debt securities available for sale	33	20
Total other debt securities | Capital trust notes
Assets:
Total debt securities available for sale	91	90
Recurring
Assets:
Total securities	8,736	9,074
Mortgage servicing rights	1,135	1,033
Total assets at fair value	11,380	11,451
Liabilities:
Total liabilities at fair value	107	136
Recurring | Commercial and industrial
Assets:
Loans held-for-sale	9
Recurring | Mortgage Loans: | Residential first mortgage loans
Assets:
Loans held-for-sale	1,148	1,115
Recurring | Interest rate swaps and swaptions
Assets:
Derivative assets	140	182
Liabilities:
Derivative liabilities	79	65
Recurring | Futures
Assets:
Derivative assets	1	2
Recurring | Rate lock commitments
Assets:
Derivative assets	6	9
Liabilities:
Derivative liabilities	12	10
Recurring | Mortgage-backed securities forwards
Assets:
Derivative assets	37	36
Liabilities:
Derivative liabilities	16	61
Recurring | Total debt securities available for sale
Assets:
Total debt securities available for sale	8,723	9,060
Recurring | Total mortgage-related debt securities
Assets:
Total debt securities available for sale	5,689	4,789
Recurring | Total mortgage-related debt securities | GSE certificates
Assets:
Total debt securities available for sale	1,164	1,297
Recurring | Total mortgage-related debt securities | GSE CMOs
Assets:
Total debt securities available for sale	4,351	3,301
Recurring | Total mortgage-related debt securities | Private Label CMOs
Assets:
Total debt securities available for sale	174	191
Recurring | Total other debt securities
Assets:
Total debt securities available for sale	3,034	4,271
Recurring | Total other debt securities | U. S. Treasury obligations
Assets:
Total debt securities available for sale	195	1,487
Recurring | Total other debt securities | GSE debentures
Assets:
Total debt securities available for sale	1,659	1,398
Recurring | Total other debt securities | Asset-backed securities
Assets:
Total debt securities available for sale	313	361
Recurring | Total other debt securities | Municipal bonds
Assets:
Total debt securities available for sale	6	30
Recurring | Total other debt securities | Corporate bonds
Assets:
Total debt securities available for sale	737	885
Recurring | Total other debt securities | Foreign notes
Assets:
Total debt securities available for sale	33	20
Recurring | Total other debt securities | Capital trust notes
Assets:
Total debt securities available for sale	91	90
Recurring | Total equity securities
Assets:
Total equity securities	13	14
Recurring | Total equity securities | Mutual funds and common stock
Assets:
Total equity securities	13	14
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Total securities	195	1,487
Mortgage servicing rights	0	0
Total assets at fair value	195	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
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Rate lock commitments
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	195	1,487
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Total mortgage-related debt securities
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Total mortgage-related debt securities | GSE certificates
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Total mortgage-related debt securities | GSE CMOs
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Total mortgage-related debt securities | Private Label CMOs
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Total other debt securities
Assets:
Total debt securities available for sale	195	1,487
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Total other debt securities | U. S. Treasury obligations
Assets:
Total debt securities available for sale	195	1,487
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Total other debt securities | GSE debentures
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Total other debt securities | Asset-backed securities
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Total other debt securities | Municipal bonds
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Total other debt securities | Corporate bonds
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Total other debt securities | Foreign notes
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Total other debt securities | Capital trust notes
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Total equity securities
Assets:
Total equity securities	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Total equity securities | Mutual funds and common stock
Assets:
Total equity securities	0	0
Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Total securities	8,509	7,587
Mortgage servicing rights	0	0
Total assets at fair value	10,012	8,922
Liabilities:
Total liabilities at fair value	95	126
Recurring | Significant Other Observable Inputs (Level 2) | Acquisition, development, and construction
Assets:
Loans held-for-sale	168
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	1,148	1,115
Recurring | Significant Other Observable Inputs (Level 2) | Interest rate swaps and swaptions
Assets:
Derivative assets	140	182
Liabilities:
Derivative liabilities	79	65
Recurring | Significant Other Observable Inputs (Level 2) | Futures
Assets:
Derivative assets	1	2
Recurring | Significant Other Observable Inputs (Level 2) | Rate lock commitments
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0	0
Recurring | Significant Other Observable Inputs (Level 2) | Mortgage-backed securities forwards
Assets:
Derivative assets	37	36
Liabilities:
Derivative liabilities	16	61
Recurring | Significant Other Observable Inputs (Level 2) | Total debt securities available for sale
Assets:
Total debt securities available for sale	8,496	7,573
Recurring | Significant Other Observable Inputs (Level 2) | Total mortgage-related debt securities
Assets:
Total debt securities available for sale	5,657	4,789
Recurring | Significant Other Observable Inputs (Level 2) | Total mortgage-related debt securities | GSE certificates
Assets:
Total debt securities available for sale	1,164	1,297
Recurring | Significant Other Observable Inputs (Level 2) | Total mortgage-related debt securities | GSE CMOs
Assets:
Total debt securities available for sale	4,351	3,301
Recurring | Significant Other Observable Inputs (Level 2) | Total mortgage-related debt securities | Private Label CMOs
Assets:
Total debt securities available for sale	142	191
Recurring | Significant Other Observable Inputs (Level 2) | Total other debt securities
Assets:
Total debt securities available for sale	2,839	2,784
Recurring | Significant Other Observable Inputs (Level 2) | Total other debt securities | U. S. Treasury obligations
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Other Observable Inputs (Level 2) | Total other debt securities | GSE debentures
Assets:
Total debt securities available for sale	1,659	1,398
Recurring | Significant Other Observable Inputs (Level 2) | Total other debt securities | Asset-backed securities
Assets:
Total debt securities available for sale	313	361
Recurring | Significant Other Observable Inputs (Level 2) | Total other debt securities | Municipal bonds
Assets:
Total debt securities available for sale	6	30
Recurring | Significant Other Observable Inputs (Level 2) | Total other debt securities | Corporate bonds
Assets:
Total debt securities available for sale	737	885
Recurring | Significant Other Observable Inputs (Level 2) | Total other debt securities | Foreign notes
Assets:
Total debt securities available for sale	33	20
Recurring | Significant Other Observable Inputs (Level 2) | Total other debt securities | Capital trust notes
Assets:
Total debt securities available for sale	91	90
Recurring | Significant Other Observable Inputs (Level 2) | Total equity securities
Assets:
Total equity securities	13	14
Recurring | Significant Other Observable Inputs (Level 2) | Total equity securities | Mutual funds and common stock
Assets:
Total equity securities	13	14
Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Total securities	32	0
Mortgage servicing rights	1,135	1,033
Total assets at fair value	1,173	1,042
Liabilities:
Total liabilities at fair value	12	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
Recurring | Significant Unobservable Inputs (Level 3) | Rate lock commitments
Assets:
Derivative assets	6	9
Liabilities:
Derivative liabilities	12	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) | Total mortgage-related debt securities
Assets:
Total debt securities available for sale	32	0
Recurring | Significant Unobservable Inputs (Level 3) | Total mortgage-related debt securities | GSE certificates
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Total mortgage-related debt securities | GSE CMOs
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Total mortgage-related debt securities | Private Label CMOs
Assets:
Total debt securities available for sale	32	0
Recurring | Significant Unobservable Inputs (Level 3) | Total other debt securities
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Total other debt securities | U. S. Treasury obligations
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Total other debt securities | GSE debentures
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Total other debt securities | Asset-backed securities
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Total other debt securities | Municipal bonds
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Total other debt securities | Corporate bonds
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Total other debt securities | Foreign notes
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Total other debt securities | Capital trust notes
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Total equity securities
Assets:
Total equity securities	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Total equity securities | Mutual funds and common stock
Assets:
Total equity securities	$ 0	$ 0