Fair Value Measures - Financial Instruments Carried at Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Assets:
Total debt securities available for sale	$ 14,823	$ 10,402
Total mortgage-related debt securities
Assets:
Total debt securities available for sale	12,112	8,573
GSE CMOs
Assets:
Total debt securities available for sale	10,942	7,304
GSE certificates
Assets:
Total debt securities available for sale	1,011	1,106
Private label CMOs
Assets:
Total debt securities available for sale	159	163
Total other debt securities
Assets:
Total debt securities available for sale	2,711	1,829
GSE debentures
Assets:
Total debt securities available for sale	1,262	1,203
U. S. treasury obligations
Assets:
Total debt securities available for sale	1,013
Asset-backed securities
Assets:
Total debt securities available for sale	222	236
Corporate bonds
Assets:
Total debt securities available for sale	167	308
Municipal bonds, foreign notes, and capital trust
Assets:
Total debt securities available for sale	5	5
Recurring
Assets:
Total securities	14,837	10,416
Mortgage servicing rights		26
Total assets at fair value	15,175	11,031
Liabilities:
Total liabilities at fair value	30	35
Recurring | Interest rate swaps
Assets:
Derivative assets	17	15
Liabilities:
Derivative liabilities	22
Recurring | Interest rate swaps and swaptions
Liabilities:
Derivative liabilities		30
Recurring | Rate lock commitments
Assets:
Derivative assets	4	3
Liabilities:
Derivative liabilities	3	3
Recurring | Mortgage-backed securities forwards
Assets:
Derivative assets		7
Liabilities:
Derivative liabilities	5	2
Recurring | Commercial real estate
Assets:
Loans held for sale	175	182
Recurring | One-to-four family first mortgage
Assets:
Loans held for sale	142	382
Recurring | Total debt securities available for sale
Assets:
Total debt securities available for sale	14,823	10,402
Recurring | Total mortgage-related debt securities
Assets:
Total debt securities available for sale	12,112	8,573
Recurring | GSE CMOs
Assets:
Total debt securities available for sale	10,942	7,304
Recurring | GSE certificates
Assets:
Total debt securities available for sale	1,011	1,106
Recurring | Private label CMOs
Assets:
Total debt securities available for sale	159	163
Recurring | Total other debt securities
Assets:
Total debt securities available for sale	2,711	1,829
Recurring | GSE debentures
Assets:
Total debt securities available for sale	1,262	1,203
Recurring | U. S. treasury obligations
Assets:
Total debt securities available for sale	1,013
Recurring | Asset-backed securities
Assets:
Total debt securities available for sale	222	236
Recurring | Corporate bonds
Assets:
Total debt securities available for sale	167	308
Recurring | Municipal bonds, foreign notes, and capital trust
Assets:
Total debt securities available for sale	47	82
Recurring | Total 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	1,013	0
Mortgage servicing rights		0
Total assets at fair value	1,013	0
Liabilities:
Total liabilities at fair value	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate swaps
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate swaps and swaptions
Liabilities:
Derivative liabilities		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
Liabilities:
Derivative liabilities	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial real estate
Assets:
Loans held for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | One-to-four family first mortgage
Assets:
Loans held for sale	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	1,013	0
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) | GSE CMOs
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 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	1,013	0
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) | U. S. treasury obligations
Assets:
Total debt securities available for sale	1,013
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) | Corporate bonds
Assets:
Total debt securities available for sale	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal bonds, foreign notes, and capital trust
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) | Mutual funds and common stock
Assets:
Total equity securities	0	0
Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Total securities	13,793	10,383
Mortgage servicing rights		0
Total assets at fair value	14,127	10,969
Liabilities:
Total liabilities at fair value	27	32
Recurring | Significant Other Observable Inputs (Level 2) | Interest rate swaps
Assets:
Derivative assets	17	15
Liabilities:
Derivative liabilities	22
Recurring | Significant Other Observable Inputs (Level 2) | Interest rate swaps and swaptions
Liabilities:
Derivative liabilities		30
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		7
Liabilities:
Derivative liabilities	5	2
Recurring | Significant Other Observable Inputs (Level 2) | Commercial real estate
Assets:
Loans held for sale	175	182
Recurring | Significant Other Observable Inputs (Level 2) | One-to-four family first mortgage
Assets:
Loans held for sale	142	382
Recurring | Significant Other Observable Inputs (Level 2) | Total debt securities available for sale
Assets:
Total debt securities available for sale	13,779	10,369
Recurring | Significant Other Observable Inputs (Level 2) | Total mortgage-related debt securities
Assets:
Total debt securities available for sale	12,081	8,540
Recurring | Significant Other Observable Inputs (Level 2) | GSE CMOs
Assets:
Total debt securities available for sale	10,942	7,304
Recurring | Significant Other Observable Inputs (Level 2) | GSE certificates
Assets:
Total debt securities available for sale	1,011	1,106
Recurring | Significant Other Observable Inputs (Level 2) | Private label CMOs
Assets:
Total debt securities available for sale	128	130
Recurring | Significant Other Observable Inputs (Level 2) | Total other debt securities
Assets:
Total debt securities available for sale	1,698	1,829
Recurring | Significant Other Observable Inputs (Level 2) | GSE debentures
Assets:
Total debt securities available for sale	1,262	1,203
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) | Asset-backed securities
Assets:
Total debt securities available for sale	222	236
Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds
Assets:
Total debt securities available for sale	167	308
Recurring | Significant Other Observable Inputs (Level 2) | Municipal bonds, foreign notes, and capital trust
Assets:
Total debt securities available for sale	47	82
Recurring | Significant Other Observable Inputs (Level 2) | Total 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)(1)
Assets:
Total securities	31	33
Mortgage servicing rights		26
Total assets at fair value	35	62
Liabilities:
Total liabilities at fair value	3	3
Recurring | Significant Unobservable Inputs (Level 3)(1) | Interest rate swaps
Assets:
Derivative assets	0	0
Liabilities:
Derivative liabilities	0
Recurring | Significant Unobservable Inputs (Level 3)(1) | Interest rate swaps and swaptions
Liabilities:
Derivative liabilities		0
Recurring | Significant Unobservable Inputs (Level 3)(1) | Rate lock commitments
Assets:
Derivative assets	4	3
Liabilities:
Derivative liabilities	3	3
Recurring | Significant Unobservable Inputs (Level 3)(1) | Mortgage-backed securities forwards
Assets:
Derivative assets		0
Liabilities:
Derivative liabilities	0	0
Recurring | Significant Unobservable Inputs (Level 3)(1) | Commercial real estate
Assets:
Loans held for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3)(1) | One-to-four family first mortgage
Assets:
Loans held for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3)(1) | Total debt securities available for sale
Assets:
Total debt securities available for sale	31	33
Recurring | Significant Unobservable Inputs (Level 3)(1) | Total mortgage-related debt securities
Assets:
Total debt securities available for sale	31	33
Recurring | Significant Unobservable Inputs (Level 3)(1) | GSE CMOs
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3)(1) | GSE certificates
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3)(1) | Private label CMOs
Assets:
Total debt securities available for sale	31	33
Recurring | Significant Unobservable Inputs (Level 3)(1) | Total other debt securities
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3)(1) | GSE debentures
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3)(1) | U. S. treasury obligations
Assets:
Total debt securities available for sale	0
Recurring | Significant Unobservable Inputs (Level 3)(1) | Asset-backed securities
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3)(1) | Corporate bonds
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3)(1) | Municipal bonds, foreign notes, and capital trust
Assets:
Total debt securities available for sale	0	0
Recurring | Significant Unobservable Inputs (Level 3)(1) | Total equity securities
Assets:
Total equity securities	0	0
Recurring | Significant Unobservable Inputs (Level 3)(1) | Mutual funds and common stock
Assets:
Total equity securities	$ 0	$ 0