DEBT (Details) (USD $)	3 Months Ended		6 Months Ended			3 Months Ended	6 Months Ended		6 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended			3 Months Ended
	Dec. 31, 2012	Jun. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Mar. 31, 2012	Dec. 31, 2012 Senior Notes Due 2017 [Member]	Sep. 30, 2012 Senior Notes Due 2017 [Member]	Mar. 31, 2012 Senior Notes Due 2017 [Member]	Sep. 30, 2012 Term Loan [Member]	Mar. 31, 2012 Term Loan [Member]	Sep. 30, 2012 Revolving Credit Facility [Member]	Mar. 31, 2012 Revolving Credit Facility [Member]	Sep. 30, 2012 Convertible Senior Notes Due 2038 [Member]	Sep. 30, 2011 Convertible Senior Notes Due 2038 [Member]	Sep. 30, 2012 Convertible Senior Notes Due 2038 [Member]	Sep. 30, 2011 Convertible Senior Notes Due 2038 [Member]	Mar. 31, 2012 Convertible Senior Notes Due 2038 [Member]	Dec. 31, 2012 Senior Notes Due 2022 [Member]	Dec. 31, 2012 364 Day Term Loan Credit Facility [Member]
Debt Instrument [Line Items]
Total debt			$ 734,686,000		$ 757,245,000		$ 350,315,000	$ 350,346,000	$ 240,000,000	$ 245,000,000	$ 40,000,000	$ 59,300,000	$ 104,371,000		$ 104,371,000		$ 102,599,000
Less short-term borrowings and current maturities of long-term debt			(18,750,000)		(14,375,000)
Long-term debt, less current maturities			715,936,000		742,870,000
Repayment of debt			24,300,000	32,518,000					5,000,000		19,300,000
Proceeds from borrowings			0	88,493,000
Debt Instrument, Interest Rate, Stated Percentage							7.50%	7.50%					3.00%		3.00%		3.00%	6.25%
Unamortized premium							300,000	300,000
Balances Of Debt And Equity Components [Abstract]
Equity component- net carrying value													14,905,000		14,905,000		14,905,000
Debt component- face amount at maturity													115,000,000		115,000,000		115,000,000
Debt component- unamortized discount													(10,629,000)		(10,629,000)		(12,401,000)
Debt component- net carrying value													104,371,000		104,371,000		102,599,000
Long Term Convertible Debt Current And Noncurrent [Abstract]
Debt discount amortization period															three year
Debt Instrument, Convertible, Effective Interest Rate		6.90%	6.90%
Contractual coupon interest													863,000	863,000	1,726,000	1,726,000
Amortization of debt discount			1,772,000	1,666,000									903,000	844,000	1,772,000	1,666,000
Total interest expense													1,766,000	1,707,000	3,498,000	3,392,000
Term Loan Credit Facility [Abstract]
Debt instrument initial amount																		450,000,000	225,000,000
Base rate description																			“Base Rate” means the higher of (1) the per annum rate the administrative agent publicly announces as its prime lending rate in effect from time to time and (2) the Federal Funds rate plus 0.50% per annum. The applicable margin ranges from 0.00% to 2.25%, depending on whether the Base Rate or LIBOR is used, and is determined based on our leverage ratio pricing grid. Until delivery of the financial statements for the three months ended September 30, 2012, the applicable margins on Base Rate and LIBOR borrowings will be 1.00% and 2.00%, respectively
364 Day Term Loan Maturity Date																			Sep. 30, 2013
Debt Instrument, Collateral	Obligations under the 364-Day Credit Agreement are guaranteed by certain of the our principal domestic subsidiaries (the “Guarantor Subsidiaries”) and secured by the U.S. cash and cash equivalents, accounts receivable, inventories, non-aircraft equipment, prepaid expenses and other current assets, intangible assets and intercompany promissory notes held by the Company and the Guarantor Subsidiaries and 100% and 65% of the capital stock of certain of our principal domestic and foreign subsidiaries, respectively. The notes will initially be jointly and severally guaranteed on a senior unsecured basis by the Guarantor Subsidiaries.
Senior Notes [Abstract]
Tender Offer Amount							350,000,000
Tender Offer Consideration Rate							up to $1,041.50 per $1,000 principal amount
Debt Instrument, Repurchase Amount						337,900,000
Initial Total Consideration Paid						352,000,000
Consideration Paid Expiration Tender							200,000
Redemption Premium Rate							1.0375%
Remaining Consideration Paid						11,900,000
Redemption Premium						15,200,000
Unamortized Debt Issuance Expense						2,700,000
Debt Instrument Issuance Date																		October 12, 2012	October 1, 2012
Debt Instrument, Priority																		These notes are unsecured senior obligations and rank effectively junior in right of payment to all our existing and future secured indebtedness, rank equal in right of payment with our existing and future senior unsecured indebtedness and rank senior in right of payment to any of our existing and future subordinated indebtedness. The notes will initially be jointly and severally guaranteed on a senior unsecured basis by the Guarantor Subsidiaries.
Debt Instrument, Collateral	Obligations under the 364-Day Credit Agreement are guaranteed by certain of the our principal domestic subsidiaries (the “Guarantor Subsidiaries”) and secured by the U.S. cash and cash equivalents, accounts receivable, inventories, non-aircraft equipment, prepaid expenses and other current assets, intangible assets and intercompany promissory notes held by the Company and the Guarantor Subsidiaries and 100% and 65% of the capital stock of certain of our principal domestic and foreign subsidiaries, respectively. The notes will initially be jointly and severally guaranteed on a senior unsecured basis by the Guarantor Subsidiaries.
Debt Instrument, Restrictive Covenants																		The indenture for the 6¼% Senior Notes includes restrictive covenants which limit, among other things, our ability to incur additional debt, issue disqualified stock, pay dividends, repurchase stock, invest in other entities, sell assets, incur additional liens or security, merge of consolidate the Company and enter into transactions with affiliates.
Debt instrument interest payment dates																		April 15 and October 15
Prepayment premium description																		We may redeem any of the notes at any time on or after October 15, 2017, in whole or part, in cash, at certain redemption prices plus accrued and unpaid interest, if any, to the date of redemption. At any time prior to October 15, 2015, we may redeem up to 35% of the aggregate principal amount of the notes issued under the indenture with the net proceeds of certain equity offerings at a redemption price equal to 106.250% of the principal amount of the notes plus accrued and unpaid interest, if any, to the date of redemption. We may make that redemption only if, after the redemption, at least 65% of the aggregate principal amount of notes issued under the indenture remains outstanding. In addition, at any time prior to October 15, 2017, we may redeem all, but not less than all, of the notes at a redemption price equal to the principal amount plus an applicable premium and accrued and unpaid interest, if any to the redemption date.
Debt Instrument, Fee Amount																		$ 7,300,000