SUPPLEMENTAL BALANCE SHEET INFORMATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Reserve for bad debt:
Balance at the beginning of the period	$ 2,696	$ 6,181	$ 4,597
Provision for bad debt	2,016		6,034
(Recovery of) bad debt		(2,013)
Write-off of bad debt	1,009
(Recovery of) write-off of bad debt		(1,472)	(4,450)
Balance at the end of the period	5,721	2,696	$ 6,181
Accounts receivable, net of reserve:
Trade receivables	398,348	286,998
Income tax receivable	78,726	37,971
Insurance recovery receivable		50,200
Total accounts receivable, net of reserve	477,074	375,169
Prepaid expenses and other current assets:
Restricted cash	32,439	27,566
Deferred mobilization	6,458	9,913
Prepaid insurance	4,060	4,354
Prepaid value added tax	3,870	1,407
Prepaid income taxes		26,138
Other	8,293	8,689
Total prepaid expenses and other current assets	55,120	78,067
Accrued liabilities:
Accrued operating costs	36,949	17,009
Payroll and employee benefits	54,941	43,547
Taxes payable, other than income tax	35,638	31,443
Self-insurance liabilities	22,159	14,801
Deferred income	25,893	34,681
Deferred mobilization	9,828	17,923
Accrued income taxes	8,011
Litigation and claims	1,779	70,535
Other	13,485	4,700
Total accrued liabilities	208,683	234,639
Noncurrent liabilities - Other:
Pension and other non-qualified retirement plans	37,989	39,762
Self-insurance liabilities	29,037	21,651
Contingent earnout liability	14,879
Deferred mobilization	7,689	24,781
Uncertain tax positions including interest and penalties	3,562	12,502
Other	8,253	4,085
Total noncurrent liabilities - other	$ 101,409	$ 102,781