Fair Value - Schedule of Fair Value Measurements on a Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	$ 873	$ 849
Investment securities available for sale	71,086	70,070
Derivative, collateral, cash offset	(3,166)	(776)
Derivative collateral, cash offset	(856)	(1,118)
Collateralized loan obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	1,810	1,760
Non-US debt securities, covered bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	3,380	3,180
Non-U.S. debt securities, other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	741	613
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	873	849
Investment securities available for sale	71,086	70,070
Derivative asset, gross liability and obligation to return cash, offset	(10,861)	(6,679)
Derivative assets	5,813	4,777
Other assets	114	2
Assets, fair value disclosure	77,886	75,698
Derivative liability, gross asset and obligation to return cash, offset	(8,551)	(7,021)
Derivative liabilities	7,585	4,132
Other liabilities	114	2
Total	7,817	4,233
Recurring | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading liabilities	3	5
Recurring | Other U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading liabilities	21	18
Recurring | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading liabilities	94	76
Recurring | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, gross liability and obligation to return cash, offset	(10,543)	(6,562)
Derivative assets	5,757	4,754
Derivative liability, gross asset and obligation to return cash, offset	(8,508)	(6,995)
Derivative liabilities	7,278	3,873
Recurring | Interest-rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, gross liability and obligation to return cash, offset	(316)	(115)
Derivative assets	55	20
Derivative liability, gross asset and obligation to return cash, offset	(41)	(24)
Derivative liabilities	165	158
Recurring | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, gross liability and obligation to return cash, offset	(2)	(2)
Derivative assets	1	3
Derivative liability, gross asset and obligation to return cash, offset	(2)	(2)
Derivative liabilities	142	101
Recurring | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	51	32
Recurring | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	486	479
Recurring | Other U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	336	338
Investment securities available for sale	2,231	2,624
Recurring | US Treasury and federal agencies, direct obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	6,342	5,718
Recurring | US Treasury and federal agencies, mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	18,234	18,165
Recurring | Asset-backed securities, student loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	6,817	7,176
Recurring | Asset-backed securities, credit cards
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	1,368	1,341
Recurring | Asset-backed securities, sub-prime
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	388	419
Recurring | Asset-backed securities, other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	1,813	1,764
Recurring | Total asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	10,386	10,700
Recurring | Non-U.S. debt securities, mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	7,612	7,071
Recurring | Non-U.S. debt securities, asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	2,704	3,267
Recurring | Government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	5,070	4,355
Recurring | Non-U.S. debt securities, other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	5,009	4,834
Recurring | Total non-U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	20,395	19,527
Recurring | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	10,026	9,746
Recurring | Collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	2,938	2,987
Recurring | U.S. equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	40	39
Recurring | Non-U.S. equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	3	3
Recurring | U.S. money-market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	473	542
Recurring | Non-U.S. money-market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	18	19
Quoted Market Prices in Active Markets (Level 1) | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	541	521
Investment securities available for sale	5,848	5,206
Derivative asset	0	0
Other assets	114	2
Assets, fair value disclosure	6,503	5,729
Derivative liability	0	0
Other liabilities	114	2
Total	219	88
Quoted Market Prices in Active Markets (Level 1) | Recurring | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading liabilities	3	5
Quoted Market Prices in Active Markets (Level 1) | Recurring | Other U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading liabilities	8	5
Quoted Market Prices in Active Markets (Level 1) | Recurring | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading liabilities	94	76
Quoted Market Prices in Active Markets (Level 1) | Recurring | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liability	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | Interest-rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liability	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liability	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	51	32
Quoted Market Prices in Active Markets (Level 1) | Recurring | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	486	479
Quoted Market Prices in Active Markets (Level 1) | Recurring | Other U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	4	10
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | US Treasury and federal agencies, direct obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	5,848	5,206
Quoted Market Prices in Active Markets (Level 1) | Recurring | US Treasury and federal agencies, mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | Asset-backed securities, student loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | Asset-backed securities, credit cards
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | Asset-backed securities, sub-prime
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | Asset-backed securities, other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | Total asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | Non-U.S. debt securities, mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | Non-U.S. debt securities, asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | Government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | Non-U.S. debt securities, other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | Total non-U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | Collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | U.S. equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | Non-U.S. equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | U.S. money-market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Quoted Market Prices in Active Markets (Level 1) | Recurring | Non-U.S. money-market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	332	328
Investment securities available for sale	62,403	62,400
Derivative asset	16,674	11,451
Other assets	0	0
Assets, fair value disclosure	79,409	74,179
Derivative liability	16,136	11,148
Other liabilities	0	0
Total	16,149	11,161
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading liabilities	0	0
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Other U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading liabilities	13	13
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading liabilities	0	0
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	16,300	11,311
Derivative liability	15,786	10,863
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Interest-rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	371	135
Derivative liability	206	182
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	3	5
Derivative liability	144	103
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	0	0
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	0	0
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Other U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	332	328
Investment securities available for sale	2,231	2,614
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | US Treasury and federal agencies, direct obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	494	512
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | US Treasury and federal agencies, mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	17,934	18,165
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Asset-backed securities, student loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	6,631	6,987
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Asset-backed securities, credit cards
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	1,368	1,341
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Asset-backed securities, sub-prime
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	388	419
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Asset-backed securities, other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Total asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	8,387	8,747
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Non-U.S. debt securities, mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	7,612	7,071
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Non-U.S. debt securities, asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	2,577	3,093
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	5,070	4,355
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Non-U.S. debt securities, other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	4,714	4,579
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Total non-U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	19,973	19,098
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	9,994	9,713
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	2,856	2,948
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | U.S. equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	40	39
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Non-U.S. equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	3	3
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | U.S. money-market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	473	542
Pricing Methods with Significant Observable Market Inputs (Level 2) | Recurring | Non-U.S. money-market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	18	19
Pricing Methods with Significant Unobservable Market Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	2,835	2,469
Total		5
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	0	0
Investment securities available for sale	2,835	2,464
Derivative asset	0	5
Other assets	0	0
Assets, fair value disclosure	2,835	2,469
Derivative liability	0	5
Other liabilities	0	0
Total	0	5
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading liabilities	0	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Other U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading liabilities	0	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading liabilities	0	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	5
Derivative liability	0	5
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Interest-rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liability	0	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liability	0	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	0	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	$ 0	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Other U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets		0
Investment securities available for sale	$ 0	10
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | US Treasury and federal agencies, direct obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | US Treasury and federal agencies, mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	300	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Asset-backed securities, student loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	186	189
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Asset-backed securities, credit cards
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Asset-backed securities, sub-prime
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Asset-backed securities, other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	1,813	1,764
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Total asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	1,999	1,953
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Non-U.S. debt securities, mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Non-U.S. debt securities, asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	127	174
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Non-U.S. debt securities, other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	295	255
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Total non-U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	422	429
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	32	33
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	82	39
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | U.S. equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Non-U.S. equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | U.S. money-market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Recurring | Non-U.S. money-market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	$ 0	$ 0