Consolidated Statements of Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of shares of common stock issued under stock option plan	97,471	104,277	167,675
Number of common stock shares purchased	205,983	76,790	43,835
Common stock	$ 0.93	$ 0.86	$ 0.78
Common Stock [Member]
Number of shares of common stock issued under stock option plan	97,471	104,277	167,675
Additional Paid-in Capital [Member]
Number of shares of common stock issued under stock option plan	97,471	104,277	167,675
Treasury Stock [Member]
Number of common stock shares purchased	205,983	76,790	43,835