BUSINESS SEGMENT AND GEOGRAPHIC INFORMATION - Total assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018
Segment information
Assets	$ 6,144,341	$ 6,214,867
Operating segment
Segment information
Assets	5,691,446	5,656,332
Investments and corporate operations
Segment information
Assets	452,895	558,535
U.S. Land | Operating segment
Segment information
Assets	5,076,230	5,012,378
Offshore | Operating segment
Segment information
Assets	103,650	105,439
International Land | Operating segment
Segment information
Assets	328,718	362,033
H&P Technologies | Operating segment
Segment information
Assets	153,170	146,957
Other.. | Operating segment
Segment information
Assets	29,678	29,525
Continued operations
Segment information
Assets	$ 6,144,341	$ 6,214,867