Goodwill and Other Intangible Assets - Rollforward of Goodwill (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Roll Forward]
Goodwill, Beginning Balance	$ 2,255	$ 2,249
Goodwill (deductions) additions	7	6
Goodwill, Ending Balance	2,262	2,255
Community Banking
Goodwill [Roll Forward]
Goodwill, Beginning Balance	2,231	2,228
Goodwill (deductions) additions	0	3
Goodwill, Ending Balance	2,231	2,231
Wealth Management
Goodwill [Roll Forward]
Goodwill, Beginning Balance	8	8
Goodwill (deductions) additions	0	0
Goodwill, Ending Balance	8	8
Insurance
Goodwill [Roll Forward]
Goodwill, Beginning Balance	16	11
Goodwill (deductions) additions	7	5
Goodwill, Ending Balance	23	16
Other
Goodwill [Roll Forward]
Goodwill, Beginning Balance	0	2
Goodwill (deductions) additions	0	(2)
Goodwill, Ending Balance	$ 0	$ 0