EMPLOYEE BENEFIT PLANS (Details 2) - USD ($) $ in Thousands	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
PLAN ASSETS
Fair value of plan assets	$ 98,060	$ 108,157	$ 96,818
Oil and Gas Properties
PLAN ASSETS
Fair value of plan assets	387	301	$ 287
Quoted Prices in Active Markets for Identical Assets (Level 1)
PLAN ASSETS
Fair value of plan assets	97,673	107,856
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments.
PLAN ASSETS
Fair value of plan assets	2,248	2,250
Quoted Prices in Active Markets for Identical Assets (Level 1) | Mutual funds:
PLAN ASSETS
Fair value of plan assets	78,060	88,507
Quoted Prices in Active Markets for Identical Assets (Level 1) | Domestic stock funds
PLAN ASSETS
Fair value of plan assets	40,072	55,054
Quoted Prices in Active Markets for Identical Assets (Level 1) | Bond funds
PLAN ASSETS
Fair value of plan assets	25,344	24,722
Quoted Prices in Active Markets for Identical Assets (Level 1) | International stock funds
PLAN ASSETS
Fair value of plan assets	12,644	8,731
Quoted Prices in Active Markets for Identical Assets (Level 1) | Domestic common stock
PLAN ASSETS
Fair value of plan assets	15,883	15,733
Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign equity stock
PLAN ASSETS
Fair value of plan assets	1,482	1,366
Significant Unobservable Inputs (Level 3)
PLAN ASSETS
Fair value of plan assets	387	301
Significant Unobservable Inputs (Level 3) | Oil and Gas Properties
PLAN ASSETS
Fair value of plan assets	387	301
Total Measure at Fair Value
PLAN ASSETS
Fair value of plan assets	98,060	108,157
Total Measure at Fair Value | Short-term investments.
PLAN ASSETS
Fair value of plan assets	2,248	2,250
Total Measure at Fair Value | Mutual funds:
PLAN ASSETS
Fair value of plan assets	78,060	88,507
Total Measure at Fair Value | Domestic stock funds
PLAN ASSETS
Fair value of plan assets	40,072	55,054
Total Measure at Fair Value | Bond funds
PLAN ASSETS
Fair value of plan assets	25,344	24,722
Total Measure at Fair Value | International stock funds
PLAN ASSETS
Fair value of plan assets	12,644	8,731
Total Measure at Fair Value | Domestic common stock
PLAN ASSETS
Fair value of plan assets	15,883	15,733
Total Measure at Fair Value | Foreign equity stock
PLAN ASSETS
Fair value of plan assets	1,482	1,366
Total Measure at Fair Value | Oil and Gas Properties
PLAN ASSETS
Fair value of plan assets	$ 387	$ 301