Statements of Income/(Loss) - Parent Company Only (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Interest and Dividend Income, Securities, Available-for-sale		$ 774	$ 651		$ 593
Interest Expense, Long-term Debt		288	260		252
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest		2,814	2,692		2,707
Income Tax Expense (Benefit)		(532)	(805)		(764)
Net Income (Loss) Attributable to Parent		2,273	1,878	[1]	1,933	[2]
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		1	(356)		(338)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent		2,274	1,522		1,595
Net Income (Loss) Available to Common Stockholders, Basic		2,179	1,811		1,863
Parent Company [Member]
Interest and Dividend Income, Securities, Available-for-sale	[3]	1,414	1,300		1,159
Interest and Fee Income, Other Loans		25	15		8
Interest Income, Deposits with Other Federal Home Loan Banks		22	12		5
Other Income		5	2		9
Revenues		1,466	1,329		1,181
Interest Expense, Short-term Borrowings		4	2		1
Interest Expense, Long-term Debt		137	140		128
Labor and Related Expense	[4]	103	57		69
Fees and Commission Expense		12	12		6
Other Expenses		33	24		21
Operating Expenses		289	235		225
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest		1,177	1,094		956
Income Tax Expense (Benefit)		72	59		61
Income (Loss) Before Equity in Undistributed Earnings of Subsidiaries		1,249	1,153		1,017
Equity in Undistributed Earnings of Subsidiaries		1,024	725		916
Net Income (Loss) Attributable to Parent		2,273	1,878		1,933
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		1	(356)		(338)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent		$ 2,274	$ 1,522		$ 1,595

[1] Beginning in the second quarter of 2017, the Company realigned its business segment structure from three segments to two segments. Specifically, the Company retained the previous composition of the Wholesale Banking segment and changed the basis of presentation of the Consumer Banking and Private Wealth Management segment and Mortgage Banking segment such that those segments were combined into a single Consumer segment. Accordingly, business segment information presented for the year ended December 31, 2016 has been revised to conform to the new business segment structure and updated internal funds transfer pricing methodology for consistent presentation.

[2] Beginning in the second quarter of 2017, the Company realigned its business segment structure from three segments to two segments. Specifically, the Company retained the previous composition of the Wholesale Banking segment and changed the basis of presentation of the Consumer Banking and Private Wealth Management segment and Mortgage Banking segment such that those segments were combined into a single Consumer segment. Accordingly, business segment information presented for the year ended December 31, 2015 has been revised to conform to the new business segment structure and updated internal funds transfer pricing methodology for consistent presentation.

[3] Substantially all dividend income is from subsidiaries (primarily the Bank).

[4] Includes incentive compensation allocations between the Parent Company and subsidiaries.