Consolidated Statements of Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Number of shares of common stock issued under stock option plan	167,675	45,289	67,029
Number of common stock shares purchased	43,835	41,915	60,595
Common stock	$ 0.78	$ 0.73	$ 0.69
Common Stock [Member]
Number of shares of common stock issued under stock option plan	167,675	45,289	67,029
Additional Paid-in Capital [Member]
Number of shares of common stock issued under stock option plan	167,675	45,289	67,029
Treasury Stock [Member]
Number of common stock shares purchased	43,835	41,915	60,595