NET INCOME PER COMMON SHARE AND EQUITY PER COMMON SHARE (Details) - $ / shares	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2014
Shares used in computing basic and diluted net income per share [Abstract]
Weighted average common shares outstanding during the period for Basic computation (in shares)	9,066,000	8,917,000
Dilutive effect of employee stock options (in shares)	64,000	38,000
Weighted average common shares outstanding during the period for Diluted computation (in shares)	9,130,000	8,955,000
Common stock excluded from calculations of diluted net income per share (in shares)	0
Class A Stock [Member]
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	15,000,000
Common stock, shares issued (in shares)	8,191,397	8,038,721
Common stock, shares outstanding (in shares)	8,191,397	8,038,721
Common stock, par value (in dollars per share)	$ 1.00
Common stock, shares issued during period (in shares)	15,184	8,044
Equity per common share (in dollars per share)	$ 14.73		$ 14.77
Class B Stock [Member]
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	1,040,000
Common stock, shares outstanding (in shares)	881,452	881,452
Common stock, par value (in dollars per share)	$ 1.00
Common stock, shares issued during period (in shares)	881,452	881,452