EARNINGS PER SHARE DATA (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Basic [Abstract]
Weighted average shares outstanding (in shares)													14,439	14,374	14,301
Net income	$ 16,900	$ 16,400	$ 13,700	$ 13,200	$ 14,100	$ 13,100	$ 12,200	$ 11,600	$ 9,200	$ 8,300	$ 7,600	$ 6,300	$ 60,237	$ 50,985	$ 31,437
Convertible preferred stock dividend													(90)	(90)	(90)
Net income attributable to common shareholders													60,147	50,895	31,347
Per share amount (in dollars per share)	$ 1.17	$ 1.13	$ 0.95	$ 0.92	$ 0.98	$ 0.91	$ 0.84	$ 0.81	$ 0.64	$ 0.58	$ 0.53	$ 0.44	$ 4.17	$ 3.54	$ 2.19
Diluted [Abstract]
Weighted average shares outstanding (in shares)													14,439	14,374	14,301
Assumed conversion of convertible preferred stock (in shares)													840	840	840
Total dilutive shares (in shares)													15,279	15,214	15,141
Net income attributable to common shareholders													60,147	50,895	31,347
Convertible preferred stock dividend													90	90	90
Net income for diluted earnings per share													$ 60,237	$ 50,985	$ 31,437
Per share amount (in dollars per share)	$ 1.10	$ 1.07	$ 0.90	$ 0.87	$ 0.92	$ 0.86	$ 0.80	$ 0.77	$ 0.61	$ 0.55	$ 0.50	$ 0.42	$ 3.94	$ 3.35	$ 2.08