Derivatives and Hedging Activities - Effect of Fair Value and Cash Flow Hedges on Income (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense — Long-term debt		$ (71)	$ (120)	$ (161)	$ (240)
Interest income — Loans		980	1,082	2,006	2,148
Deposits		(96)	(223)	(265)	(425)
Other income	[1]	33	17	(55)	27
Interest rate | Interest expense – long-term debt | Fair Value Hedging
Net gains (losses) on fair value hedging relationships
Recognized on hedged items		(5)	(152)	(299)	(245)
Recognized on derivatives designated as hedging instruments		39	142	350	224
Net income (expense) recognized on fair value hedges		34	(10)	51	(21)
Interest rate | Interest expense – long-term debt | Cash Flow Hedging
Net gain (loss) on cash flow hedging relationships
Realized gains (losses) (pre-tax) reclassified from AOCI into net income		(1)	0	(2)	(1)
Net income (expense) recognized on cash flow hedges		(1)	0	(2)
Interest rate | Interest income – loans | Fair Value Hedging
Net gains (losses) on fair value hedging relationships
Recognized on hedged items		0	0	0	0
Recognized on derivatives designated as hedging instruments		0	0	0	0
Net income (expense) recognized on fair value hedges		0	0	0	0
Interest rate | Interest income – loans | Cash Flow Hedging
Net gain (loss) on cash flow hedging relationships
Realized gains (losses) (pre-tax) reclassified from AOCI into net income		90	(19)	124	(43)
Net income (expense) recognized on cash flow hedges		90	(19)	124
Interest rate | Interest expense - deposits | Fair Value Hedging
Net gains (losses) on fair value hedging relationships
Recognized on hedged items		0	(1)	0	(1)
Recognized on derivatives designated as hedging instruments		0	0	0	0
Net income (expense) recognized on fair value hedges		0	(1)	0	(1)
Interest rate | Interest expense - deposits | Cash Flow Hedging
Net gain (loss) on cash flow hedging relationships
Realized gains (losses) (pre-tax) reclassified from AOCI into net income		0	0	0	0
Net income (expense) recognized on cash flow hedges		0	0	0
Interest rate | Other income | Fair Value Hedging
Net gains (losses) on fair value hedging relationships
Recognized on hedged items		0	0	0	0
Recognized on derivatives designated as hedging instruments		0	0	0	0
Net income (expense) recognized on fair value hedges		0	0	0	0
Interest rate | Other income | Cash Flow Hedging
Net gain (loss) on cash flow hedging relationships
Realized gains (losses) (pre-tax) reclassified from AOCI into net income		0	0	0	$ 0
Net income (expense) recognized on cash flow hedges		$ 0	$ 0	$ 0

[1] For the three months ended June 30, 2020, we had no net securities gains (losses). For the six months ended June 30, 2020, net securities gains (losses) totaled $4 million. For the three and six months ended June 30, 2019, net securities gains (losses) totaled less than $1 million. For the three months ended June 30, 2020, and June 30, 2019, we did not have any impairment losses related to securities.