Business and Summary of Significant Accounting Policies - Other intangible assets (Details)	12 Months Ended
Dec. 31, 2017 USD ($)
Finite Lived Intangible Assets [Line Items]
Core deposit intangibles amortization period (in years)	10 years
Core Deposits
Finite Lived Intangible Assets [Line Items]
Impairment on intangible assets	$ 0

The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of a finite-lived intangible asset to fair value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16373-109275

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