Consolidated Statements of Changes In Shareholders' Equity (Parenthetical) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Stockholders Equity [Abstract]
Stock issued during period, shares, Employee Stock Purchase Plans	3,578	4,465	4,162
Stock issued during period shares, Director Stock Purchase Plans	1,345
Stock issued during period, shares, acquisitions			723,851
Stock issued during period, shares, Restricted stock activity	3,996	2,115	875