EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Numerator:
Earnings available to common shares	$ 11,639	$ 13,242	$ 5,530	$ 10,415	$ 9,289	$ 12,789	$ 13,092	$ 16,492	$ 40,826	$ 51,662	$ 49,458
Denominator:
Weighted average common shares (Denominator for basic calculation, in shares)	22,920,000	23,120,000	22,768,000	22,508,000	22,816,000	23,119,000	23,032,000	22,710,000	22,506,000	22,896,000	23,084,000
Weighted average effect of dilutive securities:
Share-based compensation (in shares)									774,000	539,000	189,000
Diluted weighted average common shares (Denominator for diluted calculation, in shares)	23,706,000	23,939,000	23,780,000	22,926,000	23,191,000	23,797,000	23,693,000	23,131,000	23,280,000	23,435,000	23,273,000
Earnings per share:
Basic (in dollars per share)	$ 0.5100	$ 0.5700	$ 0.2400	$ 0.4600	$ 0.4100	$ 0.5500	$ 0.5700	$ 0.7300	$ 1.8100	$ 2.2600	$ 2.1400
Diluted (in dollars per share)	$ 0.4900	$ 0.5500	$ 0.2300	$ 0.4500	$ 0.4000	$ 0.5400	$ 0.5500	$ 0.7100	$ 1.7500	$ 2.2000	$ 2.1300
Outstanding stock options excluded from diluted earnings (in shares)									1,300,000	1,300,000	2,600,000