DEBT (Details) (USD $)	1 Months Ended	3 Months Ended	6 Months Ended		1 Months Ended	3 Months Ended		6 Months Ended			1 Months Ended	6 Months Ended	1 Months Ended	6 Months Ended	1 Months Ended		6 Months Ended	1 Months Ended			0 Months Ended	1 Months Ended	3 Months Ended		6 Months Ended					1 Months Ended		0 Months Ended	1 Months Ended	3 Months Ended	6 Months Ended	1 Months Ended		6 Months Ended			1 Months Ended	3 Months Ended		6 Months Ended				1 Months Ended					0 Months Ended		3 Months Ended	6 Months Ended	0 Months Ended
	Aug. 31, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Oct. 31, 2011 Credit Agreement	Sep. 30, 2013 Credit Agreement	Sep. 30, 2012 Credit Agreement	Sep. 30, 2013 Credit Agreement	Sep. 30, 2012 Credit Agreement	Mar. 31, 2013 Credit Agreement	Oct. 31, 2011 Credit Agreement Minimum	Sep. 30, 2013 Credit Agreement Minimum	Oct. 31, 2011 Credit Agreement Maximum	Sep. 30, 2013 Credit Agreement Base rate	Oct. 31, 2011 Credit Agreement Base rate Minimum	Oct. 31, 2011 Credit Agreement Base rate Maximum	Sep. 30, 2013 Credit Agreement LIBOR	Oct. 31, 2011 Credit Agreement LIBOR Minimum	Oct. 31, 2011 Credit Agreement LIBOR Maximum	Sep. 30, 2013 Letter of Credit	Aug. 29, 2013 4.375% Convertible Notes Due 2014	Jun. 30, 2009 4.375% Convertible Notes Due 2014	Sep. 30, 2013 4.375% Convertible Notes Due 2014	Sep. 30, 2012 4.375% Convertible Notes Due 2014	Sep. 30, 2013 4.375% Convertible Notes Due 2014	Sep. 30, 2012 4.375% Convertible Notes Due 2014	Aug. 31, 2013 4.375% Convertible Notes Due 2014	Jun. 12, 2013 4.375% Convertible Notes Due 2014	Mar. 31, 2013 4.375% Convertible Notes Due 2014	Jun. 30, 2009 4.375% Convertible Notes Due 2014 4.375% Convertible Note hedge options	Jun. 30, 2009 4.375% Convertible Notes Due 2014 4.375% Convertible Note hedge warrants	Aug. 29, 2013 4.375% Convertible Notes Due 2014 Maximum	Jun. 30, 2009 4.375% Convertible Notes Due 2014 Conversion Terms at Holder's Option	Sep. 30, 2013 4.375% Convertible Notes Due 2014 Conversion Terms at Holder's Option	Sep. 30, 2013 4.375% Convertible Notes Due 2014 Conversion Terms at Holder's Option	Jun. 30, 2009 4.375% Convertible Notes Due 2014 Conversion Terms at Holder's Option Minimum D	Jun. 30, 2009 4.375% Convertible Notes Due 2014 Conversion Terms at Holder's Option Maximum D	Sep. 30, 2013 4.375% Convertible Notes Due 2014 Redemption Terms at Company Option	Sep. 30, 2013 4.375% Convertible Notes Due 2014 Redemption Terms at Company Option Minimum	Sep. 30, 2013 4.375% Convertible Notes Due 2014 Redemption Terms at Company Option Maximum	Nov. 30, 2011 1.75% Convertible Notes Due 2016	Sep. 30, 2013 1.75% Convertible Notes Due 2016	Sep. 30, 2012 1.75% Convertible Notes Due 2016	Sep. 30, 2013 1.75% Convertible Notes Due 2016	Sep. 30, 2012 1.75% Convertible Notes Due 2016	Mar. 31, 2013 1.75% Convertible Notes Due 2016	Nov. 16, 2011 1.75% Convertible Notes Due 2016	Nov. 30, 2011 1.75% Convertible Notes Due 2016 Conversion Terms at Holder's Option	Nov. 30, 2011 1.75% Convertible Notes Due 2016 Conversion Terms at Holder's Option Minimum D	Nov. 30, 2011 1.75% Convertible Notes Due 2016 Conversion Terms at Holder's Option Maximum D	Nov. 30, 2011 1.75% Convertible Notes Due 2016 Conversion Terms upon Occurrence of Certain Fundamental Company Changes	Nov. 30, 2011 1.75% Convertible Notes Due 2016 Conversion Terms, Event of Default	Jul. 17, 2013 1.00% Convertible Notes Due 2018	Jun. 18, 2013 1.00% Convertible Notes Due 2018	Sep. 30, 2013 1.00% Convertible Notes Due 2018	Sep. 30, 2013 1.00% Convertible Notes Due 2018	Jun. 18, 2013 1.00% Convertible Notes Due 2018 Maximum	Jun. 18, 2013 1.00% Convertible Notes Due 2018 Conversion Terms at Holder's Option	Jun. 18, 2013 1.00% Convertible Notes Due 2018 Conversion Terms at Holder's Option Minimum D	Jun. 18, 2013 1.00% Convertible Notes Due 2018 Conversion Terms at Holder's Option Maximum D	Jun. 18, 2013 1.00% Convertible Notes Due 2018 Conversion Terms upon Occurrence of Certain Fundamental Company Changes	Jun. 18, 2013 1.00% Convertible Notes Due 2018 Conversion Terms, Event of Default
Credit Agreement
Maximum borrowing capacity					$ 100,000,000															$ 25,000,000
Amount of additional borrowings by which maximum borrowing capacity may be increased					40,000,000
Interest rate, variable rate basis														Base Rate			LIBOR
Interest rate added to base rate (as a percent)															1.50%	2.00%		2.50%	3.00%
Interest rate at end of period (as a percent)														4.75%			2.68%
Monthly fee on unused available balance (as a percent)											0.375%		0.50%
Outstanding borrowings						0		0		0
Credit Agreement Availability
Available borrowings						70,736,000		70,736,000		73,565,000
Outstanding letters of credit						1,664,000		1,664,000		1,664,000
Interest expense and fees						160,000	160,000	319,000	319,000
Interest coverage ratio												1
Trailing period for measurement of interest coverage ratio								12 months
Maximum liquidity level triggering the requirement to maintain an interest coverage ratio of one to one								30,000,000
Convertible Notes
Aggregate principal amount																						138,000,000																									250,000,000							250,000,000
Interest rate on convertible notes (as a percent)																						4.375%	4.375%		4.375%		4.375%															1.75%		1.75%			1.75%							1.00%	1.00%	1.00%
Percentage of par value at which debt was issued																																																						98.50%
Period of overallotment option to purchase additional amount of debt granted to underwriters																																																						30 days
Additional amount of debt for purchase of which overallotment option is granted to underwriters																																																									37,500,000
Amount pertaining to exercise of over-allotment of debt by underwriters																						18,000,000																															37,500,000
Proceeds from issuance of debt			283,188,000																																																		283,188,000	246,250,000
Initial conversion rate of common stock per $1000 of principal amount of Convertible Notes (in shares)																						93.6768																			52.3745													46.4727
Principal amount used for debt instrument conversion ratio																						1,000																									1,000							1,000
Initial conversion price of convertible notes into common stock (in dollars per share)																						$ 10.675	$ 10.675		$ 10.675																						$ 19.093							$ 21.52
Number of shares to be converted into common stock																						12,927,000																			13,094,000													13,361,000
Number of trading days triggering conversion of redemption feature																																				20 days	30 days		20 days	30 days									20 days	30 days									20 days	30 days
Target ratio of closing share price to conversion price as a condition for conversion or redemption of Convertible Notes (as a percent)																																	130.00%					150.00%										130.00%										130.00%
Number of trading days in the measurement period that the entity's common stock closing price to conversion price must exceed a specified percentage of conversion price to trigger conversion feature of notes																																				5	10												5	10									5	10
Ratio of closing share price to conversion price as a condition for conversion of Convertible Notes (as a percent)																																	98.00%															98.00%										98.00%
Redemption price as percentage of principal amount of notes plus accrued and unpaid interest																																						100.00%
Redemption price as percentage of principal amount of notes plus accrued and unpaid interest																																																			100.00%										100.00%
Minimum percentage of aggregate principal amount held by bondholders to declare notes due and payable																																																				25.00%										25.00%
In event of default arising out of certain bankruptcy events, the percentage of principal amount due and payable																																																				100.00%										100.00%
Derivative nonmonetary notional amount (in shares)																														12,927,000
Investment options exercise price (in dollars per share)																														$ 10.675
Total cost charged to additional paid-in capital for options to purchase common stock																														43,600,000
Investment warrants exercise price (in dollars per share)																															$ 14.945
Number of shares of common stock that will be settled against warrants																															12,927,000
Total proceeds from warrants credited to additional paid-in capital																															26,300,000
Proceeds from unwinding of convertible note hedge	84,429,000		84,429,000
Payments to warrant holders	55,651,000		55,651,000
Estimated fair value of convertible notes																																										298,475,000		298,475,000										225,567,000	318,579,000	318,579,000
Non-convertible borrowing rate (as a percent)																																																						6.15%
Carrying amount of the equity component of convertible notes																																																						57,621,000
Banking, legal and accounting fees related to issuance of convertible notes																						3,410,000																									6,875,000							2,815,000
Banking, legal and accounting fees related to issuance of convertible notes allocated to the liability component																																									5,428,000													2,209,000
Banking, legal and accounting fees related to issuance of convertible notes allocated to the equity component																																									1,447,000													606,000
Redemption price of debt instrument for each $1 principal amount																												1
Principal amount used for ratio of debt instrument redemption price																												1
Cash payable for convertible notes surrendered for conversion in connection with the redemption on a combination settlement basis			165,999,000																		7,000											166,000,000		165,992,000
Amount of debt converted																																		137,993,000	137,993,000
Number of shares issued upon conversion																																		3,217,000
Debt redeemed																					7,000
Loss on extinguishment, net of capitalized debt issuance costs		9,014,000	9,014,000																				9,014,000		9,014,000
Loss on change in the fair value of the convertible note warrant		16,298,000	13,798,000
Gain on change in the fair value of the convertible note hedge		21,670,000	17,259,000
Additional information related to convertible notes
Additional paid-in capital																													42,018,000													51,180,000		51,180,000		51,180,000									57,621,000	57,621,000
Principal amount of Convertible Notes																												138,000,000	138,000,000													250,000,000		250,000,000		250,000,000									287,500,000	287,500,000
Unamortized discount of the liability component																													12,819,000													35,085,000		35,085,000		39,979,000									58,889,000	58,889,000
Net carrying amount of Convertible Notes																													125,181,000													214,915,000		214,915,000		210,021,000									228,611,000	228,611,000
Carrying amount of debt issuance costs																													797,000													3,262,000		3,262,000		3,821,000									2,072,000	2,072,000
Components of interest expense
Cash interest expense (coupon interest expense)																							1,007,000	1,509,000	2,516,000	3,018,000																1,094,000	1,094,000	2,188,000	2,188,000										732,000	823,000
Non-cash amortization of discount on Convertible Notes			12,296,000	9,199,000																			1,771,000	2,347,000	4,358,000	4,620,000																2,467,000	2,309,000	4,894,000	4,579,000										2,712,000	3,044,000
Amortization of debt issuance costs			1,070,000	1,017,000																			113,000	170,000	284,000	341,000																278,000	291,000	559,000	586,000										125,000	137,000
Total interest expense related to Convertible Notes																							$ 2,891,000	$ 4,026,000	$ 7,158,000	$ 7,979,000																$ 3,839,000	$ 3,694,000	$ 7,641,000	$ 7,353,000										$ 3,569,000	$ 4,004,000