Business Segments - Additional Information (Details)	12 Months Ended
Dec. 31, 2017 branch
Regional Bank
Business segments
Number of full-service branches	349

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_SegmentReportingInformationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration