Nature of Banking Activities and Significant Accounting Policies - Estimated useful lives of property and equipment (Details)	12 Months Ended
	Dec. 31, 2016
Buildings and Improvements [Member] | Minimum [Member]
Premises and Equipment [Abstract]
Estimated useful life	10 years
Buildings and Improvements [Member] | Maximum [Member]
Premises and Equipment [Abstract]
Estimated useful life	40 years
Furniture and Equipment [Member] | Minimum [Member]
Premises and Equipment [Abstract]
Estimated useful life	3 years
Furniture and Equipment [Member] | Maximum [Member]
Premises and Equipment [Abstract]
Estimated useful life	15 years