CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Statement of Stockholders' Equity [Abstract]
Cash dividends declared (in dollars per share)	$ 0.52	$ 0.52
Distribution of shares of treasury stock for directors' compensation (in shares)	6,015	7,880
Distribution of shares of treasury stock for employee stock compensation (in shares)	1,784	5,861
Distribution of shares of treasury stock for directors deferred compensation shares (in shares)	36,861	2,438
Sale of shares of treasury stock (in shares)	7,143	8,788
Restricted stock awards, forfeited (in shares)		1,139