EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016		Mar. 31, 2015
Earnings Per Share [Abstract]
Net income, as reported	$ 73,328	$ 60,903	$ 121,975		$ 184,223
Basic earnings per share
Weighted average shares of common stock outstanding-basic (shares)	85,834,000	85,328,000	85,754,000		84,940,000
Basic earnings per common share (usd per share)	$ 0.85	$ 0.71	$ 1.42		$ 2.17
Diluted earnings per share
Weighted average shares of common stock outstanding-basic (shares)	85,834,000	85,328,000	85,754,000		84,940,000
Incremental shares	1,024,000	1,042,000	1,024,000	[1]	1,042,000	[1]
Weighted average shares of common stock outstanding-diluted (shares)	86,858,000	86,370,000	86,778,000		85,982,000
Diluted earnings per common share (usd per share)	$ 0.84	$ 0.71	$ 1.41	[2]	$ 2.14	[2]
Anti-dilutive shares excluded from the calculation of diluted earnings per share	0	0	0		0

[1] Incremental shares consist primarily of unvested stock awards and performance shares.

[2] There were no anti-dilutive shares excluded from the calculation of diluted earnings per share for the three and six months ended March 31, 2016 and 2015.