Summary of Significant Accounting Policies and Nature of Operations - Schedule of Impact Resulted from ASU 2017-07 Adoption (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accounting Policies [Abstract]
Salaries and employee benefits	$ 696	$ 678	$ 1,381	$ 1,348
Other	$ 100	$ 107	$ 210	$ 199

Amount of expense for salary, wage, profit sharing; incentive and equity-based compensation; and other employee benefit.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(b)(4))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

Name:	us-gaap_LaborAndRelatedExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration