Summary of Significant Accounting Policies - Premisis and Equipment (Details)	12 Months Ended
	Dec. 31, 2018
Building and building improvements | Minimum
Property, Plant and Equipment
Property, plant and equipment, useful life	15 years
Building and building improvements | Maximum
Property, Plant and Equipment
Property, plant and equipment, useful life	40 years
Furniture, fixtures and equipment | Minimum
Property, Plant and Equipment
Property, plant and equipment, useful life	3 years
Furniture, fixtures and equipment | Maximum
Property, Plant and Equipment
Property, plant and equipment, useful life	7 years