CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Distribution of shares of treasury stock for directors' deferred compensation (in shares)	3,598	3,467	3,356
Distribution of shares of treasury stock granted for employee restricted stock awards (in shares)	7,628	11,279	8,087
Forfeit of shares of restricted stock awards (in shares)			1,797
Cash dividends declared (in dollars per share)	$ 1.04	$ 1.04	$ 1.04
Distribution of shares of treasury stock for directors' compensation (in shares)	9,673	8,385	7,969
Distribution of shares of treasury stock for employee compensation (in shares)	3,303	3,595	4,116
Sale of shares of treasury stock (in shares)	16,209		2,396
Purchase of shares of treasury stock (in shares)	1,184		3,094