SHAREHOLDERS' EQUITY (Details 2)	12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares	Dec. 31, 2013 USD ($) $ / shares
Dividends
Total earnings per weighted average share of common stock - diluted (in dollars per share | $ / shares	$ 1.29	$ 1.55	$ 1.48
Dividends paid per share (in dollars per share) | $ / shares	$ 1.04	$ 1.025	$ 1.005
Total dividends paid	$ 45,430,000	$ 44,381,000	$ 43,006,000
Retained earnings year-end balance	101,443,000	$ 90,276,000	$ 67,600,000
First quarterly dividend paid excluded from EDE Mortgage covenant	98,000
Cumulative aggregate amount up to which the entity may declare or pay any dividends as per EDE Mortgage covenant	$ 10,750,000
Maximum period for payment of dividend after the related date of declaration or notice of dividend as per EDE Mortgage covenant	60 days
Ratio of total indebtedness to total capitalization	0.625