Goodwill - Changes in Goodwill by Reporting Segment (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018	Mar. 22, 2019	Dec. 31, 2016
Goodwill [Line Items]
Goodwill			$ 1,800	$ 3,410
Accumulated impairment losses				(965)
Goodwill Roll Forward
Net carrying value, beginning of period:		$ 2,445
Acquisition activity	$ 1,809	33
Net carrying value, end of period:	4,284	2,478
Sale of Business	(3)
Commercial Banking
Goodwill [Line Items]
Goodwill				1,363
Accumulated impairment losses				(750)
Goodwill Roll Forward
Net carrying value, beginning of period:		613
Acquisition activity	0	17
Net carrying value, end of period:	630	630
Sale of Business	0
Branch Banking
Goodwill [Line Items]
Goodwill				1,655
Accumulated impairment losses				0
Goodwill Roll Forward
Net carrying value, beginning of period:		1,655
Acquisition activity	0	0
Net carrying value, end of period:	1,655	1,655
Sale of Business	0
Consumer Lending
Goodwill [Line Items]
Goodwill				215
Accumulated impairment losses				(215)
Goodwill Roll Forward
Net carrying value, beginning of period:		0
Acquisition activity	0	0
Net carrying value, end of period:	0	0
Sale of Business	0
Wealth and Asset Management
Goodwill [Line Items]
Goodwill				177
Accumulated impairment losses				0
Goodwill Roll Forward
Net carrying value, beginning of period:		177
Acquisition activity	0	16
Net carrying value, end of period:	190	193
Sale of Business	(3)
General Corporate and Other
Goodwill [Line Items]
Goodwill				0
Accumulated impairment losses				$ 0
Goodwill Roll Forward
Net carrying value, beginning of period:		0
Acquisition activity	1,809	0
Net carrying value, end of period:	1,809	$ 0
Sale of Business	$ 0