SUPPLEMENTAL BALANCE SHEET INFORMATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Reserve for bad debt:
Balance at the beginning of the period	$ 5,721	$ 2,696	$ 6,181
Provision for bad debt	2,193	2,016
(Recovery of) bad debt			(2,013)
(Write-off) of bad debt			(1,472)
Recovery of write-off of bad debt	(1,697)	1,009
Balance at the end of the period	6,217	5,721	$ 2,696
Accounts receivable, net of reserve:
Trade receivables	530,859	398,348
Income tax receivable	34,343	78,726
Total accounts receivable, net of reserve	565,202	477,074
Prepaid expenses and other current assets:
Restricted cash	39,830	32,439
Deferred mobilization	6,484	6,458
Prepaid insurance	6,149	4,060
Prepaid value added tax	1,931	3,870
Prepaid maintenance and rent	8,526	5,940
Prepaid multi-flex rig fabrication	1,327
Other	2,151	2,356
Total prepaid expenses and other current assets	66,398	55,123
Accrued liabilities:
Accrued operating costs	37,528	36,949
Payroll and employee benefits	80,915	54,941
Taxes payable, other than income tax	50,683	35,638
Self-insurance liabilities	15,887	22,159
Deferred income	20,527	25,893
Deferred mobilization	9,662	9,828
Accrued income taxes	7,375	8,011
Escrow	11,258	4,690
Litigation and claims	1,749	1,779
Other	8,920	8,869
Total accrued liabilities	244,504	208,757
Noncurrent liabilities - Other:
Pension and other non-qualified retirement plans	35,051	37,989
Self-insurance liabilities	39,380	29,037
Contingent earnout liability	11,160	14,879
Deferred mobilization	2,738	7,689
Uncertain tax positions including interest and penalties	2,870	3,562
Other	2,407	8,253
Total noncurrent liabilities - other	$ 93,606	$ 101,409