Derivatives, Derivatives in Fair Value and Cash Flow Hedging Relationships (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Line Items Presented in the Consolidated Statement of Income [Abstract]
Debt securities	$ 3,781	$ 3,594	$ 7,722	$ 7,008
Loans	11,316	10,912	22,670	21,491
Mortgage loans held for sale	195	198	347	377
Deposits (2)	(2,213)	(1,268)	(4,239)	(2,358)
Long-term debt (2)	(1,900)	(1,658)	(3,827)	(3,234)
Other	744	485	1,318	1,087
Total amounts of line items presented in the consolidated statement of income	11,923	12,263	23,991	24,371
Derivatives (Textual) [Abstract]
Cash flow hedge deferred loss in other comprehensive income			(247)
Time value component recognized as net interest income (expense) on forward derivatives excluded from the assessment of hedge effectiveness	7	2	$ 14	2
Maximum length of time hedged in cash flow hedge			7 years
Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Net income (expense) recognized on fair value hedges	(4)	(205)	$ (76)	(312)
Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Net income (expense) recognized on cash flow hedges	(79)	(77)	(158)	(137)
Interest rate contract [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Amounts related to interest settlements on derivatives	14	18	0	101
Recognized on derivatives	2,184	(499)	3,555	(2,084)
Recognized on hedged items	(2,113)	452	(3,426)	1,950
Interest rate contract [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Realized gains (losses) (pre tax) reclassified from cumulative OCI into net income	(76)	(77)	(154)	(137)
Foreign exchange contract [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Amounts related to interest settlements on derivatives	(118)	(92)	(250)	(167)
Recognized on derivatives	526	(1,311)	412	(818)
Recognized on hedged items	(497)	1,227	(367)	706
Foreign exchange contract [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Realized gains (losses) (pre tax) reclassified from cumulative OCI into net income	(3)	0	(4)	0
Debt securities [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Net income (expense) recognized on fair value hedges	30	(25)	60	(119)
Debt securities [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Net income (expense) recognized on cash flow hedges	0	0	0	0
Debt securities [Member] | Interest rate contract [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Amounts related to interest settlements on derivatives	14	(42)	30	(124)
Recognized on derivatives	(1,089)	356	(1,903)	1,306
Recognized on hedged items	1,096	(352)	1,913	(1,320)
Debt securities [Member] | Interest rate contract [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Realized gains (losses) (pre tax) reclassified from cumulative OCI into net income	0	0	0	0
Debt securities [Member] | Foreign exchange contract [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Amounts related to interest settlements on derivatives	10	10	20	15
Recognized on derivatives	(5)	2	(9)	6
Recognized on hedged items	4	1	9	(2)
Debt securities [Member] | Foreign exchange contract [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Realized gains (losses) (pre tax) reclassified from cumulative OCI into net income	0	0	0	0
Loans [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Net income (expense) recognized on fair value hedges	0	0	0	0
Loans [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Net income (expense) recognized on cash flow hedges	(77)	(77)	(155)	(137)
Loans [Member] | Interest rate contract [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Amounts related to interest settlements on derivatives	0	0	0	0
Recognized on derivatives	0	0	0	1
Recognized on hedged items	0	0	0	(1)
Loans [Member] | Interest rate contract [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Realized gains (losses) (pre tax) reclassified from cumulative OCI into net income	(77)	(77)	(155)	(137)
Loans [Member] | Foreign exchange contract [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Amounts related to interest settlements on derivatives	0	0	0	0
Recognized on derivatives	0	0	0	0
Recognized on hedged items	0	0	0	0
Loans [Member] | Foreign exchange contract [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Realized gains (losses) (pre tax) reclassified from cumulative OCI into net income	0	0	0	0
Mortgage loans held for sale [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Net income (expense) recognized on fair value hedges	(1)	(3)	(2)	(6)
Mortgage loans held for sale [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Net income (expense) recognized on cash flow hedges	0	0	0	0
Mortgage loans held for sale [Member] | Interest rate contract [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Amounts related to interest settlements on derivatives	0	(1)	0	(2)
Recognized on derivatives	(25)	5	(33)	11
Recognized on hedged items	24	(7)	31	(15)
Mortgage loans held for sale [Member] | Interest rate contract [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Realized gains (losses) (pre tax) reclassified from cumulative OCI into net income	0	0	0	0
Mortgage loans held for sale [Member] | Foreign exchange contract [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Amounts related to interest settlements on derivatives	0	0	0	0
Recognized on derivatives	0	0	0	0
Recognized on hedged items	0	0	0	0
Mortgage loans held for sale [Member] | Foreign exchange contract [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Realized gains (losses) (pre tax) reclassified from cumulative OCI into net income	0	0	0	0
Deposits [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Net income (expense) recognized on fair value hedges	1	(30)	(5)	(43)
Deposits [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Net income (expense) recognized on cash flow hedges	0	0	0	0
Deposits [Member] | Interest rate contract [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Amounts related to interest settlements on derivatives	(7)	(20)	(30)	(25)
Recognized on derivatives	351	(41)	558	(190)
Recognized on hedged items	(343)	31	(533)	172
Deposits [Member] | Interest rate contract [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Realized gains (losses) (pre tax) reclassified from cumulative OCI into net income	0	0	0	0
Deposits [Member] | Foreign exchange contract [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Amounts related to interest settlements on derivatives	0	0	0	0
Recognized on derivatives	0	0	0	0
Recognized on hedged items	0	0	0	0
Deposits [Member] | Foreign exchange contract [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Realized gains (losses) (pre tax) reclassified from cumulative OCI into net income	0	0	0	0
Long-term debt [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Net income (expense) recognized on fair value hedges	(45)	(45)	(129)	(75)
Long-term debt [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Net income (expense) recognized on cash flow hedges	(2)	0	(3)	0
Long-term debt [Member] | Interest rate contract [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Amounts related to interest settlements on derivatives	7	81	0	252
Recognized on derivatives	2,947	(819)	4,933	(3,212)
Recognized on hedged items	(2,890)	780	(4,837)	3,114
Long-term debt [Member] | Interest rate contract [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Realized gains (losses) (pre tax) reclassified from cumulative OCI into net income	1	0	1	0
Long-term debt [Member] | Foreign exchange contract [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Amounts related to interest settlements on derivatives	(128)	(102)	(270)	(182)
Recognized on derivatives	205	97	497	(74)
Recognized on hedged items	(186)	(82)	(452)	27
Long-term debt [Member] | Foreign exchange contract [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Realized gains (losses) (pre tax) reclassified from cumulative OCI into net income	(3)	0	(4)	0
Other noninterest income [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Net income (expense) recognized on fair value hedges	11	(102)	0	(69)
Other noninterest income [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Net income (expense) recognized on cash flow hedges	0	0	0	0
Other noninterest income [Member] | Interest rate contract [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Amounts related to interest settlements on derivatives	0	0	0	0
Recognized on derivatives	0	0	0	0
Recognized on hedged items	0	0	0	0
Other noninterest income [Member] | Interest rate contract [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Realized gains (losses) (pre tax) reclassified from cumulative OCI into net income	0	0	0	0
Other noninterest income [Member] | Foreign exchange contract [Member] | Fair Value Hedging [Member]
Gains (losses) on fair value hedging relationships
Amounts related to interest settlements on derivatives	0	0	0	0
Recognized on derivatives	326	(1,410)	(76)	(750)
Recognized on hedged items	(315)	1,308	76	681
Other noninterest income [Member] | Foreign exchange contract [Member] | Cash Flow Hedging [Member]
Gains (losses) on cash flow hedging relationships
Realized gains (losses) (pre tax) reclassified from cumulative OCI into net income	$ 0	$ 0	$ 0	$ 0