CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Parenthetical)	12 Months Ended
	Dec. 31, 2017 $ / shares shares	Dec. 31, 2016 $ / shares shares	Dec. 31, 2015 $ / shares shares
Statement of Stockholders' Equity [Abstract]
Cash dividends declared (in dollars per share) | $ / shares	$ 0.75	$ 0.73	$ 0.67
Treasury stock purchased (in shares)	9,603	23,072	984
Net shares issued to employee stock plans (in shares)	91,517	123,349	96,813
Stock split conversion ratio	1.5