CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Common stock dividends, shares			446,597
Treasury stock, shares			21,945
Stock dividend per dollar amount			$ 15.72
Cash dividends	$ 0.58	$ 0.54	$ 0.52