Property and Equipment - Summary of Property and Equipment by Classification (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Sep. 30, 2015
Property, Plant and Equipment
Total cost	$ 4,857,978	$ 4,815,962
Less: Accumulated depreciation	(648,420)	(643,830)
Property and equipment, net	4,209,558	4,172,132
Drilling vessels and equipment
Property, Plant and Equipment
Total cost	3,944,409	4,003,483
Construction work in progress
Property, Plant and Equipment
Total cost	818,580	720,852
Drill pipe
Property, Plant and Equipment
Total cost	55,768	55,248
Office equipment and other
Property, Plant and Equipment
Total cost	$ 39,221	$ 36,379