Consolidated Statements of Changes in Stockholders' Equity [Parenthetical] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Exercise of stock options (in shares)	53,586
Issuance of common stock (in shares)	58,445
Issuance of common stock for restricted stock awards (in shares)	6,750	7,550
Cash dividends declared on common stock (in dollars per share)	$ 1.08	$ 1.04