Investment Securities - FHLB, FRB, and other stock (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Federal Home Loan Bank Stock	$ 17,300,000
Federal Reserve Bank Stock	25,300,000
Other stock	23,300,000
Excess Federal Home Loan Bank Stock with Entity Repurchased by Federal Home Loan Bank	$ 10,300,000	$ 0	$ 16,400,000