SHARE-BASED COMPENSATION (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pretax stock based compensation cost	$ 3,030	$ 2,817	$ 2,815
Percentage of increments earned for share awards	25.00%
Restricted Stock [Member]
Shares [Roll Forward]
Outstanding, beginning of period (in shares)	558,600
Granted (in shares)	46,400
Vested (in shares)	(141,800)
Forfeited (in shares)	(38,700)
Outstanding, end of period (in shares)	424,500	558,600
Weighted Average Award Price [Roll Forward]
Outstanding, beginning of period (in dollars per share)	$ 22.64
Granted (in dollars per share)	24.05
Vested (in dollars per share)	21.59
Forfeited (in dollars per share)	21.70
Outstanding, end of period (in dollars per share)	$ 23.23	$ 22.64
Weighted Average Remaining Contractual Term [Abstract]
Outstanding	3 years	3 years 1 month 6 days
Pretax unrecognized compensation cost	$ 6,600
Period over which compensation cost is expected to be recognized	4 years 10 months 24 days
Restricted Stock [Member] | Common Class B [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issued (in shares)	46,400	180,000	84,000
2011 Equity Compensation Plan [Member] | Restricted Stock [Member] | Common Class B [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized under the plan (in shares)	1,400,000
Common shares available for future issuance (in shares)	592,100