INCOME TAXES (Details 2) (USD $)	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Reconciliation of income tax computed at the U.S. federal statutory tax rate to income tax expense
Tax at federal statutory rate	$ 41,176,000	$ 37,072,000	$ 29,834,000
State income taxes, net of federal tax effect	1,297,000	3,042,000	2,672,000
Nondeductible expenses	480,000	324,000	408,000
Change in reserve accrued for tax contingencies	625,000	(1,641,000)	(777,000)
Tax effect from foreign earnings repatriation			3,063,000
Tax effect from foreign subsidiaries	(5,347,000)	(2,212,000)	(2,523,000)
Federal R&D credits generated in the current year	(2,696,000)	(491,000)	(993,000)
Reinstatement of federal R&D credit	(1,406,000)		(794,000)
Other	(1,560,000)	(809,000)	(1,336,000)
Total income tax expense	32,569,000	35,285,000	29,554,000
Net changes in the liability for unrecognized tax benefits
Balance at the beginning of the period	3,168,000	4,809,000
Decrease related to tax positions in prior years:
Recognition of benefits from expiration of statutes	(1,172,000)	(1,747,000)
Tax positions related to the current year	1,797,000	106,000
Tax positions related to tax adjustments recorded in the entity's acquisition of Abraxas	484,000
Balance at the end of the period	4,277,000	3,168,000	4,809,000
Unrecognized tax benefits from permanent tax adjustments that, if recognized, would affect the effective rate	4,300,000
Interest and penalties accrued	200,000	200,000
Total liability for uncertain tax issues	4,500,000	3,400,000
Income tax payments, net of refunds	42,100,000	30,000,000	28,800,000
Components of income before income taxes
United States	44,955,000	60,451,000	45,329,000
Foreign	72,692,000	45,470,000	39,911,000
Income before income taxes	117,647,000	105,921,000	85,240,000
Approximate amount of undistributed earnings of all the entity's foreign subsidiaries	$ 142,000,000