Accumulated Other Comprehensive Income - Reclassifications Out of AOCI (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income — Loans		$ 4,267	$ 4,023	$ 3,677
Interest expense — Long-term debt		(454)	(420)	(319)
Investment banking and debt placement fees		630	650	603
Other income	[1]	68	176	153
Other expense		2,250	2,309	2,278
Income (loss) before income taxes and equity in net income (loss) less dividends from subsidiaries		2,054	2,234	1,981
Income taxes		314	344	637
Income (loss) from continuing operations		1,708	1,859	$ 1,291
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Securities Available for Sale [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) before income taxes and equity in net income (loss) less dividends from subsidiaries		20	0
Income taxes		5	0
Income (loss) from continuing operations		15	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) before income taxes and equity in net income (loss) less dividends from subsidiaries		46	(37)
Income taxes		11	(8)
Income (loss) from continuing operations		35	(29)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Foreign Currency Translation Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income		(14)	0
Income (loss) before income taxes and equity in net income (loss) less dividends from subsidiaries		(14)	0
Income taxes		(3)	0
Income (loss) from continuing operations		(11)	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Net Pension and Postretirement Benefit Costs [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) before income taxes and equity in net income (loss) less dividends from subsidiaries		(31)	(33)
Income taxes		(8)	(8)
Income (loss) from continuing operations		(23)	(25)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Net Pension and Postretirement Benefit Costs [Member] | Amortization of Losses [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense		(13)	(17)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Net Pension and Postretirement Benefit Costs [Member] | Settlement Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense		(18)	(17)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Net Pension and Postretirement Benefit Costs [Member] | Amortization Of Prior Service Credit [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense		0	1
Other Income [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Securities Available for Sale [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income		20	0
Other Income [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] | Foreign Exchange Contract [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income		32	31
Interest Income [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] | Interest Rate [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income — Loans		15	(68)
Interest Expense [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense — Long-term debt		(1)	(2)
Investment Banking And Debt Placement [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] | Interest Rate [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment banking and debt placement fees		$ 0	$ 2

[1] Net securities gains (losses) totaled $20 million for the year ended December 31, 2019, less than $1 million for the year ended December 31, 2018, and $1 million for the year ended December 31, 2017. For 2019, 2018, and 2017, we did not have any impairment losses related to securities.