Deposits - Additional Information (Detail) - GE Capital Bank [Member] $ in Millions	Apr. 30, 2016 USD ($)
Deposits [Line Items]
Deposits assumed	$ 16,520
Online Deposit Accounts and Certificates of Deposit [Member]
Deposits [Line Items]
Deposits assumed	8,760
Brokered Certificates Of Deposit [Member]
Deposits [Line Items]
Deposits assumed	$ 7,760

Amount of liabilities assumed at the acquisition date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4845-128472

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant