SUMMARY OF QUARTERLY RESULTS OF OPERATIONS (UNAUDITED) (Details 9) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2013 Assets and liabilities measured at fair value on a recurring basis Level 1	Sep. 30, 2012 Assets and liabilities measured at fair value on a recurring basis Level 1	Jun. 30, 2013 Assets and liabilities measured at fair value on a recurring basis Level 1 Interim Financial Information	Mar. 31, 2013 Assets and liabilities measured at fair value on a recurring basis Level 1 Interim Financial Information	Dec. 31, 2012 Assets and liabilities measured at fair value on a recurring basis Level 1 Interim Financial Information	Jun. 30, 2012 Assets and liabilities measured at fair value on a recurring basis Level 1 Interim Financial Information	Mar. 31, 2012 Assets and liabilities measured at fair value on a recurring basis Level 1 Interim Financial Information	Dec. 31, 2011 Assets and liabilities measured at fair value on a recurring basis Level 1 Interim Financial Information	Sep. 30, 2013 Assets and liabilities measured at fair value on a recurring basis Level 2	Sep. 30, 2012 Assets and liabilities measured at fair value on a recurring basis Level 2	Jun. 30, 2013 Assets and liabilities measured at fair value on a recurring basis Level 2 Interim Financial Information	Mar. 31, 2013 Assets and liabilities measured at fair value on a recurring basis Level 2 Interim Financial Information	Dec. 31, 2012 Assets and liabilities measured at fair value on a recurring basis Level 2 Interim Financial Information	Jun. 30, 2012 Assets and liabilities measured at fair value on a recurring basis Level 2 Interim Financial Information	Mar. 31, 2012 Assets and liabilities measured at fair value on a recurring basis Level 2 Interim Financial Information	Dec. 31, 2011 Assets and liabilities measured at fair value on a recurring basis Level 2 Interim Financial Information	Sep. 30, 2013 Assets and liabilities measured at fair value on a recurring basis Level 3	Jun. 30, 2013 Assets and liabilities measured at fair value on a recurring basis Level 3 Interim Financial Information	Mar. 31, 2013 Assets and liabilities measured at fair value on a recurring basis Level 3 Interim Financial Information	Dec. 31, 2012 Assets and liabilities measured at fair value on a recurring basis Level 3 Interim Financial Information	Sep. 30, 2013 Assets and liabilities measured at fair value on a recurring basis Total	Sep. 30, 2012 Assets and liabilities measured at fair value on a recurring basis Total	Jun. 30, 2013 Assets and liabilities measured at fair value on a recurring basis Total Interim Financial Information	Mar. 31, 2013 Assets and liabilities measured at fair value on a recurring basis Total Interim Financial Information	Dec. 31, 2012 Assets and liabilities measured at fair value on a recurring basis Total Interim Financial Information	Jun. 30, 2012 Assets and liabilities measured at fair value on a recurring basis Total Interim Financial Information	Mar. 31, 2012 Assets and liabilities measured at fair value on a recurring basis Total Interim Financial Information	Dec. 31, 2011 Assets and liabilities measured at fair value on a recurring basis Total Interim Financial Information
Assets
Cash equivalents		$ 125,512	$ 171,300	$ 137,981	$ 115,214	$ 128,080	$ 173,451	$ 205,862	$ 251,913													$ 125,512	$ 171,300	$ 137,981	$ 115,214	$ 128,080	$ 173,451	$ 205,862	$ 251,913
Marketable securities		4,055		4,049												7,895	18,872					4,055		4,049				7,895	18,872
Current derivative assets										1,597	3,779	3,918	2,827	2,552	648	2,197	1,000					1,597	3,779	3,918	2,827	2,552	648	2,197	1,000
Noncurrent derivative assets										6,096	3,713	6,634	5,303	2,612	4,471	3,041	2,196					6,096	3,713	6,634	5,303	2,612	4,471	3,041	2,196
Total assets measured at fair value		129,567	171,300	142,030	115,214	128,080	173,451	205,862	251,913	7,693	7,492	10,552	8,130	5,164	5,119	13,133	22,068					137,260	178,792	152,582	123,344	133,244	178,570	218,995	273,981
Liabilities
Current derivative liabilities										2,360	6,839	3,469	6,809	5,564	3,071	1,687	5,955					2,360	6,839	3,469	6,809	5,564	3,071	1,687	5,955
Noncurrent derivative liabilities										5,366	6,498	5,694	7,170	4,304	7,010	6,497	5,246					5,366	6,498	5,694	7,170	4,304	7,010	6,497	5,246
Contingent consideration to Seller of NEK																			11,104	11,684	11,684			11,104	11,684	11,684
Total liabilities measured at fair value										7,726	13,337	9,163	13,979	9,868	10,081	8,184	11,201	3,485	11,104	11,684	11,684	11,211	13,337	20,267	25,663	21,552	10,081	8,184	11,201
Period in which amount of contingent consideration will be due	12 months
Change in the fair value of the contingent consideration	$ 0