Loans and Related Allowance for Credit Losses, Credit Quality Indicators for Residential Mortgage Loans by Vintage (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable Textual [Abstract]
High value properties, threshold	$ 1.5
Total Consumer [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total loans	384,456.0		$ 389,255.0
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Loan charge-offs, loans	1,021.0	$ 774.0
Total Consumer [Member] | Residential mortgage [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	1,942.0		13,203.0
Term loans by origination year, fiscal year before current fiscal year, finance receivable	12,824.0		46,168.0
Term loans by origination year, two years before current fiscal year, finance receivable	45,618.0		62,638.0
Term loans by origination year, three years before current fiscal year, finance receivable	61,918.0		35,257.0
Term loans by origination year, four years before current fiscal year, finance receivable	34,806.0		19,520.0
Term loans by origination year, more than five years before current fiscal year, finance receivable	86,166.0		68,742.0
Revolving loans, finance receivable	7,398.0		8,109.0
Revolving loans converted to term loans, finance receivable	6,950.0		7,087.0
Total loans	257,622.0		260,724.0
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, charge-offs	0.0		0.0
Term loans by origination year, fiscal year before current fiscal year, charge-offs	0.0		1.0
Term loans by origination year, two years before current fiscal year, charge-offs	0.0		0.0
Term loans by origination year, three years before current fiscal year, charge-offs	1.0		0.0
Term loans by origination year, four years before current fiscal year, charge-offs	0.0		2.0
Term loans by origination year, more than five years before current fiscal year, charge-offs	11.0		63.0
Revolving loans, charge-offs	0.0		4.0
Revolving loans converted to term loans, charge-offs	7.0		66.0
Loan charge-offs, loans	19.0	$ 28.0	136.0
Total Consumer [Member] | Residential mortgage [Member] | Not government insured/guaranteed [Member] | LTV 0-80% [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	1,936.0		12,434.0
Term loans by origination year, fiscal year before current fiscal year, finance receivable	11,588.0		39,624.0
Term loans by origination year, two years before current fiscal year, finance receivable	39,371.0		61,421.0
Term loans by origination year, three years before current fiscal year, finance receivable	60,654.0		34,833.0
Term loans by origination year, four years before current fiscal year, finance receivable	34,320.0		19,123.0
Term loans by origination year, more than five years before current fiscal year, finance receivable	78,302.0		61,043.0
Revolving loans, finance receivable	7,271.0		7,903.0
Revolving loans converted to term loans, finance receivable	6,795.0		6,923.0
Total loans	240,237.0		243,304.0
Total Consumer [Member] | Residential mortgage [Member] | Not government insured/guaranteed [Member] | LTV 80.01-100% [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	5.0		687.0
Term loans by origination year, fiscal year before current fiscal year, finance receivable	1,140.0		6,286.0
Term loans by origination year, two years before current fiscal year, finance receivable	6,012.0		1,065.0
Term loans by origination year, three years before current fiscal year, finance receivable	1,119.0		232.0
Term loans by origination year, four years before current fiscal year, finance receivable	306.0		203.0
Term loans by origination year, more than five years before current fiscal year, finance receivable	400.0		207.0
Revolving loans, finance receivable	98.0		103.0
Revolving loans converted to term loans, finance receivable	106.0		114.0
Total loans	9,186.0		8,897.0
Total Consumer [Member] | Residential mortgage [Member] | Not government insured/guaranteed [Member] | LTV greater than 100% [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	0.0		51.0
Term loans by origination year, fiscal year before current fiscal year, finance receivable	64.0		193.0
Term loans by origination year, two years before current fiscal year, finance receivable	167.0		57.0
Term loans by origination year, three years before current fiscal year, finance receivable	59.0		33.0
Term loans by origination year, four years before current fiscal year, finance receivable	23.0		31.0
Term loans by origination year, more than five years before current fiscal year, finance receivable	53.0		38.0
Revolving loans, finance receivable	17.0		21.0
Revolving loans converted to term loans, finance receivable	24.0		24.0
Total loans	407.0		448.0
Total Consumer [Member] | Residential mortgage [Member] | Not government insured/guaranteed [Member] | No LTV available [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	1.0		26.0
Term loans by origination year, fiscal year before current fiscal year, finance receivable	26.0		50.0
Term loans by origination year, two years before current fiscal year, finance receivable	49.0		56.0
Term loans by origination year, three years before current fiscal year, finance receivable	49.0		62.0
Term loans by origination year, four years before current fiscal year, finance receivable	58.0		51.0
Term loans by origination year, more than five years before current fiscal year, finance receivable	185.0		154.0
Revolving loans, finance receivable	12.0		82.0
Revolving loans converted to term loans, finance receivable	25.0		26.0
Total loans	405.0		507.0
Total Consumer [Member] | Residential mortgage [Member] | Not government insured/guaranteed [Member] | FICO 740 or more [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	1,838.0		12,243.0
Term loans by origination year, fiscal year before current fiscal year, finance receivable	11,872.0		42,550.0
Term loans by origination year, two years before current fiscal year, finance receivable	42,080.0		58,827.0
Term loans by origination year, three years before current fiscal year, finance receivable	58,246.0		33,232.0
Term loans by origination year, four years before current fiscal year, finance receivable	32,807.0		18,000.0
Term loans by origination year, more than five years before current fiscal year, finance receivable	67,363.0		50,938.0
Revolving loans, finance receivable	5,780.0		6,291.0
Revolving loans converted to term loans, finance receivable	4,023.0		4,092.0
Total loans	224,009.0		226,173.0
Total Consumer [Member] | Residential mortgage [Member] | Not government insured/guaranteed [Member] | FICO 700 to 739 [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	95.0		679.0
Term loans by origination year, fiscal year before current fiscal year, finance receivable	649.0		2,324.0
Term loans by origination year, two years before current fiscal year, finance receivable	2,265.0		2,510.0
Term loans by origination year, three years before current fiscal year, finance receivable	2,400.0		1,219.0
Term loans by origination year, four years before current fiscal year, finance receivable	1,223.0		888.0
Term loans by origination year, more than five years before current fiscal year, finance receivable	5,180.0		4,478.0
Revolving loans, finance receivable	806.0		883.0
Revolving loans converted to term loans, finance receivable	935.0		979.0
Total loans	13,553.0		13,960.0
Total Consumer [Member] | Residential mortgage [Member] | Not government insured/guaranteed [Member] | FICO 660 to 699 [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	8.0		185.0
Term loans by origination year, fiscal year before current fiscal year, finance receivable	203.0		843.0
Term loans by origination year, two years before current fiscal year, finance receivable	826.0		861.0
Term loans by origination year, three years before current fiscal year, finance receivable	821.0		422.0
Term loans by origination year, four years before current fiscal year, finance receivable	397.0		310.0
Term loans by origination year, more than five years before current fiscal year, finance receivable	2,468.0		2,261.0
Revolving loans, finance receivable	383.0		417.0
Revolving loans converted to term loans, finance receivable	597.0		601.0
Total loans	5,703.0		5,900.0
Total Consumer [Member] | Residential mortgage [Member] | Not government insured/guaranteed [Member] | FICO 620 to 659 [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	0.0		45.0
Term loans by origination year, fiscal year before current fiscal year, finance receivable	33.0		227.0
Term loans by origination year, two years before current fiscal year, finance receivable	205.0		179.0
Term loans by origination year, three years before current fiscal year, finance receivable	182.0		110.0
Term loans by origination year, four years before current fiscal year, finance receivable	114.0		66.0
Term loans by origination year, more than five years before current fiscal year, finance receivable	1,043.0		978.0
Revolving loans, finance receivable	139.0		150.0
Revolving loans converted to term loans, finance receivable	309.0		322.0
Total loans	2,025.0		2,077.0
Total Consumer [Member] | Residential mortgage [Member] | Not government insured/guaranteed [Member] | FICO less than 620 [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	0.0		11.0
Term loans by origination year, fiscal year before current fiscal year, finance receivable	29.0		122.0
Term loans by origination year, two years before current fiscal year, finance receivable	131.0		100.0
Term loans by origination year, three years before current fiscal year, finance receivable	119.0		64.0
Term loans by origination year, four years before current fiscal year, finance receivable	56.0		46.0
Term loans by origination year, more than five years before current fiscal year, finance receivable	1,310.0		1,245.0
Revolving loans, finance receivable	172.0		174.0
Revolving loans converted to term loans, finance receivable	479.0		464.0
Total loans	2,296.0		2,226.0
Total Consumer [Member] | Residential mortgage [Member] | Not government insured/guaranteed [Member] | No FICO available [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	1.0		35.0
Term loans by origination year, fiscal year before current fiscal year, finance receivable	32.0		87.0
Term loans by origination year, two years before current fiscal year, finance receivable	92.0		122.0
Term loans by origination year, three years before current fiscal year, finance receivable	113.0		113.0
Term loans by origination year, four years before current fiscal year, finance receivable	110.0		98.0
Term loans by origination year, more than five years before current fiscal year, finance receivable	1,576.0		1,542.0
Revolving loans, finance receivable	118.0		194.0
Revolving loans converted to term loans, finance receivable	607.0		629.0
Total loans	2,649.0		2,820.0
Total Consumer [Member] | Residential mortgage [Member] | Not government insured/guaranteed [Member] | Current-29 days past due [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	1,942.0		13,192.0
Term loans by origination year, fiscal year before current fiscal year, finance receivable	12,813.0		46,065.0
Term loans by origination year, two years before current fiscal year, finance receivable	45,517.0		62,529.0
Term loans by origination year, three years before current fiscal year, finance receivable	61,789.0		35,124.0
Term loans by origination year, four years before current fiscal year, finance receivable	34,677.0		19,364.0
Term loans by origination year, more than five years before current fiscal year, finance receivable	77,851.0		60,391.0
Revolving loans, finance receivable	7,340.0		8,044.0
Revolving loans converted to term loans, finance receivable	6,617.0		6,735.0
Total loans	248,546.0		251,444.0
Total Consumer [Member] | Residential mortgage [Member] | Not government insured/guaranteed [Member] | 30 to 89 days past due [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	0.0		6.0
Term loans by origination year, fiscal year before current fiscal year, finance receivable	5.0		70.0
Term loans by origination year, two years before current fiscal year, finance receivable	59.0		58.0
Term loans by origination year, three years before current fiscal year, finance receivable	80.0		28.0
Term loans by origination year, four years before current fiscal year, finance receivable	22.0		30.0
Term loans by origination year, more than five years before current fiscal year, finance receivable	744.0		724.0
Revolving loans, finance receivable	35.0		41.0
Revolving loans converted to term loans, finance receivable	146.0		151.0
Total loans	1,091.0		1,108.0
Total Consumer [Member] | Residential mortgage [Member] | Not government insured/guaranteed [Member] | 90 days or more past due [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	0.0		0.0
Term loans by origination year, fiscal year before current fiscal year, finance receivable	0.0		18.0
Term loans by origination year, two years before current fiscal year, finance receivable	23.0		12.0
Term loans by origination year, three years before current fiscal year, finance receivable	12.0		8.0
Term loans by origination year, four years before current fiscal year, finance receivable	8.0		14.0
Term loans by origination year, more than five years before current fiscal year, finance receivable	345.0		327.0
Revolving loans, finance receivable	23.0		24.0
Revolving loans converted to term loans, finance receivable	187.0		201.0
Total loans	598.0		604.0
Total Consumer [Member] | Residential mortgage [Member] | Government insured or guaranteed [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	0.0		5.0
Term loans by origination year, fiscal year before current fiscal year, finance receivable	6.0		15.0
Term loans by origination year, two years before current fiscal year, finance receivable	19.0		39.0
Term loans by origination year, three years before current fiscal year, finance receivable	37.0		97.0
Term loans by origination year, four years before current fiscal year, finance receivable	99.0		112.0
Term loans by origination year, more than five years before current fiscal year, finance receivable	7,226.0		7,300.0
Revolving loans, finance receivable	0.0		0.0
Revolving loans converted to term loans, finance receivable	0.0		0.0
Total loans	7,387.0		7,568.0
Total Consumer [Member] | Residential mortgage [Member] | Government insured or guaranteed [Member] | 90 days or more past due [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total loans	$ 2,700.0		$ 2,600.0