SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Schedule of Revenue by Major Customers) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended																12 Months Ended
	Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Revenue, Major Customer [Line Items]
Revenues from significant customers	$ 323,373	[1]	$ 292,777	[1]	$ 273,097	[1]	$ 284,706	[1]	$ 292,721	[1]	$ 272,688	[1]	$ 253,161	[1]	$ 245,093	[1]	$ 1,173,953	$ 1,063,663	$ 787,421
Apache Energy Ltd. [Member]
Revenue, Major Customer [Line Items]
Revenues from significant customers																	209,871	159,369	0
Shell Offshore Inc. [Member]
Revenue, Major Customer [Line Items]
Revenues from significant customers																	179,763	28,349	0
Chevron Australia Pty. Ltd. [Member]
Revenue, Major Customer [Line Items]
Revenues from significant customers																	175,334	197,242	265,731
Hess Corporation [Member]
Revenue, Major Customer [Line Items]
Revenues from significant customers																	0	154,973	0
Noble Energy Inc. [Member]
Revenue, Major Customer [Line Items]
Revenues from significant customers																	169,851	153,615	137,135
Sarawak Shell Bhd. [Member]
Revenue, Major Customer [Line Items]
Revenues from significant customers																	0	0	44,405
Kosmos Energy Ghana Inc. [Member]
Revenue, Major Customer [Line Items]
Revenues from significant customers																	$ 12,933	$ 0	$ 90,088

[1] The sum of the individual quarterly earnings per common share amounts may not agree with year-to-date earnings per common share as each quarterly computation is based on the weighted-average number of common shares outstanding during that period.