Business Segments - Income (loss) from Continuing Operations Before Income Taxes (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended					6 Months Ended
	Jun. 30, 2013		Sep. 30, 2012	Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating income (loss)	$ 70,606			$ 150,894		$ 165,538		$ 308,558
Net gain (loss) on asset disposals	1,033	[1]		28,332	[1]	908	[1]	30,732	[1]
Interest income	250			179		423		233
Interest expense	(6,941)		(978)	(5,051)		(13,707)		(9,633)
Other	381			(144)		400		(89)
Income before income taxes	64,296			145,878		152,654		299,069
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating income (loss)	82,850			134,606		190,155		300,682
Operating Segments | Contract Drilling
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating income (loss)	47,069			90,536		119,618		202,307
Operating Segments | Pressure Pumping
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating income (loss)	30,254			36,846		58,769		83,633
Operating Segments | Oil and Natural Gas
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating income (loss)	5,527			7,224		11,768		14,742
Corporate and other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating income (loss)	$ (13,277)			$ (12,044)		$ (25,525)		$ (22,856)

[1] Net gains or losses associated with the disposal of assets relate to corporate strategy decisions of the executive management group. Accordingly, the related gains or losses have been separately presented and excluded from the results of specific segments.