Nature of Operations and Summary of Significant Accounting Policies - Premises and Equipment (Details)	12 Months Ended
Dec. 31, 2017
Vehicles
Premises and Equipment
Estimated useful lives	P5Y
Minimum \| Buildings
Premises and Equipment
Estimated useful lives	P10Y
Minimum \| Leasehold improvements
Premises and Equipment
Estimated useful lives	P5Y
Minimum \| Furniture, fixtures and equipment
Premises and Equipment
Estimated useful lives	P3Y
Maximum \| Buildings
Premises and Equipment
Estimated useful lives	P40Y
Maximum \| Leasehold improvements
Premises and Equipment
Estimated useful lives	P39Y
Maximum \| Furniture, fixtures and equipment
Premises and Equipment
Estimated useful lives	P10Y

Describes the periods of time over which an entity anticipates to receive utility from its property, plant and equipment (that is, the periods of time over which an entity allocates the initial cost of its property, plant and equipment).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 35
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68071081&loc=d3e1205-110223

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