DIVIDENDS, SHARE REPURCHASES AND EARNINGS PER SHARE (Details) (USD $)	3 Months Ended					6 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2013	Sep. 30, 2012
Dividends, Share Repurchases and Earnings Per Share [Line Items]
Cash dividends declared per common share		$ 0.25		$ 0.20		$ 0.50	$ 0.40
Stock repurchase authorized amount	$ 100,000,000		$ 100,000,000		$ 100,000,000
Payments for repurchase of common stock			1,200,000				25,100,000
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Income available to common stockholders - basic		110,606,000		29,668,000		137,492,000	53,330,000
Interest expense on assumed conversion of 3% Convertible Notes, net of tax		0		0		0	0
Income available to common stockholders - diluted		$ 110,606,000		$ 29,668,000		$ 137,492,000	$ 53,330,000
Weighted average number of common shares outstanding - basic		36,403,556		35,815,672		36,265,932	35,858,237
Assumed conversion of 3% Convertible Senior Noted outstanding during the period		0		0		0	0
Net effect of dilutive stock options, restricted stock units and restricted stock awards based on the treasury stock method		297,670		526,620		352,492	601,940
Weighted average number of common shares outstanding - diluted		36,701,226		36,342,292		36,618,424	36,460,177
Basic earnings per share		$ 3.04		$ 0.83		$ 3.79	$ 1.49
Diluted earnings per share		$ 3.01		$ 0.82		$ 3.75	$ 1.46
Earnings Per Share Potentially Dilutive Securities		1.5 million		1.5 million
Debt Instrument Convertible Terms Of Conversion Feature		the base conversion price of the notes was approximately $74.81, based on the base conversion rate of 13.3666 shares of Common Stock per $1,000 principal amount of convertible notes (subject to adjustment in certain circumstances, including the payment of dividends). In general, upon conversion of a note, the holder will receive cash equal to the principal amount of the note and Common Stock to the extent of the note’s conversion value in excess of such principal amount. In addition, if at the time of conversion the applicable price of our Common Stock exceeds the base conversion price, holders will receive up to an additional 8.6882 shares of our Common Stock per $1,000 principal amount of notes, as determined pursuant to a specified formula.
Debt Instrument, Convertible, Conversion Price		$ 74.81				$ 74.81
Quarter To Date [Member] | Stock Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding		596,191		552,209
Weighted average exercise price		$ 53.10		$ 43.56		$ 53.10	$ 43.56
Quarter To Date [Member] | Restricted Stock Units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding		0		4,040
Weighted average exercise price		$ 0.00		$ 53.89		$ 0.00	$ 53.89
Quarter To Date [Member] | Restricted Stock Awards [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding		0		0
Weighted average exercise price		$ 0.00		$ 0.00		$ 0.00	$ 0.00
Year To Date [Member] | Stock Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding						497,041	448,269
Weighted average exercise price		$ 50.84		$ 43.81		$ 50.84	$ 43.81
Year To Date [Member] | Restricted Stock Units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding						0	58,016
Weighted average exercise price		$ 0.00		$ 46.97		$ 0.00	$ 46.97
Year To Date [Member] | Restricted Stock Awards [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding						5,611	0
Weighted average exercise price		$ 68.31		$ 0.00		$ 68.31	$ 0.00
Dividend Declared [Member]
Dividends, Share Repurchases and Earnings Per Share [Line Items]
Cash dividends declared per common share		$ 0.25