Fair Value Measurement - Financial Instruments Carried at Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Assets:
Total debt securities available for sale	$ 10,402	$ 9,145
Mortgage servicing rights	26	1,111
Total debt securities available for sale
Assets:
Total debt securities available for sale	10,402	9,145
Mortgage-related Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	8,573	6,563
GSE collateralized mortgage obligations
Assets:
Total debt securities available for sale	7,304	5,162
GSE certificates
Assets:
Total debt securities available for sale	1,106	1,221
Private label collateralized mortgage obligations
Assets:
Total debt securities available for sale	163	180
Other Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	1,829	2,582
GSE debentures
Assets:
Total debt securities available for sale	1,203	1,609
Corporate bonds
Assets:
Total debt securities available for sale	308	343
Asset-backed securities
Assets:
Total debt securities available for sale	236	302
U. S. Treasury obligations
Assets:
Total debt securities available for sale		198
Municipal bonds
Assets:
Total debt securities available for sale	5	6
Recurring
Assets:
Total securities	10,416	9,159
Mortgage servicing rights	26	1,111
Total assets at fair value	11,031	11,310
Liabilities:
Total liabilities at fair value	35	95
Recurring | Acquisition, development, and construction
Assets:
Loans held for sale	182	123
Recurring | Commercial and industrial
Assets:
Loans held for sale		9
Recurring | Loans held for investment | Residential first mortgage loans
Assets:
Loans held for sale	382	770
Loans held for investment	0
Recurring | Interest rate swaps and swaptions
Assets:
Derivative assets	15	115
Liabilities:
Derivative liabilities	30	59
Recurring | Mortgage-backed securities forwards
Assets:
Derivative assets	7	11
Liabilities:
Derivative liabilities	2	32
Recurring | Rate lock commitments (fallout-adjusted)
Assets:
Derivative assets	3	12
Liabilities:
Derivative liabilities	3	3
Recurring | Futures
Liabilities:
Derivative liabilities		1
Recurring | Total debt securities available for sale
Assets:
Total debt securities available for sale	10,402	9,145
Recurring | Mortgage-related Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	8,573	6,563
Recurring | GSE collateralized mortgage obligations
Assets:
Total debt securities available for sale	7,304	5,162
Recurring | GSE certificates
Assets:
Total debt securities available for sale	1,106	1,221
Recurring | Private label collateralized mortgage obligations
Assets:
Total debt securities available for sale	163	180
Recurring | Other Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	1,829	2,582
Recurring | GSE debentures
Assets:
Total debt securities available for sale	1,203	1,609
Recurring | Corporate bonds
Assets:
Total debt securities available for sale	308	343
Recurring | Asset-backed securities
Assets:
Total debt securities available for sale	236	302
Recurring | U. S. Treasury obligations
Assets:
Total debt securities available for sale		198
Recurring | Municipal bonds
Assets:
Total debt securities available for sale	82	130
Recurring | Equity securities:
Assets:
Total equity securities	14	14
Recurring | Mutual funds and common stock
Assets:
Total equity securities	14	14
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Total securities	0	198
Mortgage servicing rights	0	0
Total assets at fair value	0	198
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	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) | Loans held for investment | Residential first mortgage loans
Assets:
Loans held for sale	0	0
Loans held for investment	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) | 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) | 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) | Futures
Liabilities:
Derivative liabilities		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	0	198
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 collateralized mortgage obligations
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) | Private label collateralized mortgage obligations
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	0	198
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) | Corporate bonds
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) | U. S. Treasury obligations
Assets:
Total debt securities available for sale		198
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) | Equity securities:
Assets:
Total equity securities	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mutual funds and common stock
Assets:
Total equity securities	0	0
Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Total securities	10,383	8,929
Mortgage servicing rights	0	0
Total assets at fair value	10,969	9,957
Liabilities:
Total liabilities at fair value	32	92
Recurring | Significant Other Observable Inputs (Level 2) | Acquisition, development, and construction
Assets:
Loans held for sale	182	123
Recurring | Significant Other Observable Inputs (Level 2) | Commercial and industrial
Assets:
Loans held for sale		9
Recurring | Significant Other Observable Inputs (Level 2) | Loans held for investment | Residential first mortgage loans
Assets:
Loans held for sale	382	770
Loans held for investment	0
Recurring | Significant Other Observable Inputs (Level 2) | Interest rate swaps and swaptions
Assets:
Derivative assets	15	115
Liabilities:
Derivative liabilities	30	59
Recurring | Significant Other Observable Inputs (Level 2) | Mortgage-backed securities forwards
Assets:
Derivative assets	7	11
Liabilities:
Derivative liabilities	2	32
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) | Futures
Liabilities:
Derivative liabilities		1
Recurring | Significant Other Observable Inputs (Level 2) | Total debt securities available for sale
Assets:
Total debt securities available for sale	10,369	8,915
Recurring | Significant Other Observable Inputs (Level 2) | Mortgage-related Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	8,540	6,531
Recurring | Significant Other Observable Inputs (Level 2) | GSE collateralized mortgage obligations
Assets:
Total debt securities available for sale	7,304	5,162
Recurring | Significant Other Observable Inputs (Level 2) | GSE certificates
Assets:
Total debt securities available for sale	1,106	1,221
Recurring | Significant Other Observable Inputs (Level 2) | Private label collateralized mortgage obligations
Assets:
Total debt securities available for sale	130	148
Recurring | Significant Other Observable Inputs (Level 2) | Other Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	1,829	2,384
Recurring | Significant Other Observable Inputs (Level 2) | GSE debentures
Assets:
Total debt securities available for sale	1,203	1,609
Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds
Assets:
Total debt securities available for sale	308	343
Recurring | Significant Other Observable Inputs (Level 2) | Asset-backed securities
Assets:
Total debt securities available for sale	236	302
Recurring | Significant Other Observable Inputs (Level 2) | U. S. Treasury obligations
Assets:
Total debt securities available for sale		0
Recurring | Significant Other Observable Inputs (Level 2) | Municipal bonds
Assets:
Total debt securities available for sale	82	130
Recurring | Significant Other Observable Inputs (Level 2) | Equity securities:
Assets:
Total equity securities	14	14
Recurring | Significant Other Observable Inputs (Level 2) | Mutual funds and common stock
Assets:
Total equity securities	14	14
Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Total securities	33	32
Mortgage servicing rights	26	1,111
Total assets at fair value	62	1,155
Liabilities:
Total liabilities at fair value	3	3
Recurring | Significant Unobservable Inputs (Level 3) | Acquisition, development, and construction
Assets:
Loans held for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Commercial and industrial
Assets:
Loans held for sale		0
Recurring | Significant Unobservable Inputs (Level 3) | Loans held for investment | Residential first mortgage loans
Assets:
Loans held for sale	0	0
Loans held for investment	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) | Mortgage-backed securities forwards
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Rate lock commitments (fallout-adjusted)
Assets:
Derivative assets	3	12
Liabilities:
Derivative liabilities	3	3
Recurring | Significant Unobservable Inputs (Level 3) | Futures
Liabilities:
Derivative liabilities		0
Recurring | Significant Unobservable Inputs (Level 3) | Total debt securities available for sale
Assets:
Total debt securities available for sale	33	32
Recurring | Significant Unobservable Inputs (Level 3) | Mortgage-related Debt Securities Available for Sale:
Assets:
Total debt securities available for sale	33	32
Recurring | Significant Unobservable Inputs (Level 3) | GSE collateralized mortgage obligations
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | GSE certificates
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Private label collateralized mortgage obligations
Assets:
Total debt securities available for sale	33	32
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) | GSE debentures
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) | Asset-backed securities
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
Recurring | Significant Unobservable Inputs (Level 3) | Municipal bonds
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Equity securities:
Assets:
Total equity securities	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Mutual funds and common stock
Assets:
Total equity securities	$ 0	$ 0