Industry Segment Information (Industry Segment Information) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Revenues:
Oil and natural gas	$ 198,498		$ 164,799		$ 386,705		$ 318,408
Contract drilling	135,782		118,660		260,040		238,013
Elimination of inter-segment revenue	(21,504)		(13,655)		(39,162)		(25,480)
Contract drilling net of inter-segment revenue	114,278		105,005		220,878		212,533
Gas gathering and processing	116,354		92,910		236,714		173,066
Elimination of inter-segment revenue	(23,699)		(22,293)		(50,878)		(45,054)
Gas gathering and processing net of inter-segment revenue	92,655		70,617		185,836		128,012
Total revenues	405,431		340,421		793,419		658,953
Operating income
Oil and natural gas	82,530		64,470		170,642		123,058
Contract drilling	27,545		23,507		51,946		47,773
Gas gathering and processing	3,898		2,846		6,528		3,675
Total operating income	113,973	[1]	90,823	[1]	229,116	[1]	174,506	[1]
General and administrative expense	(10,600)		(9,679)		(20,237)		(18,352)
Gain on disposition of assets	195		3,483		9,621		3,399
Gain (loss) on derivatives not designated as hedges and hedge ineffectiveness, net	(10,709)		16,344		(29,075)		10,420
Interest expense, net	(4,131)		(4,591)		(7,921)		(8,152)
Other	(49)		(91)		71		(157)
Income before income taxes	$ 88,679		$ 96,289		$ 181,575		$ 161,664

[1] Operating income is total operating revenues less operating expenses, depreciation, depletion, amortization, and impairment and does not include general corporate expenses, gain on disposition of assets, gain (loss) on non-designated hedges and hedge ineffectiveness, interest expense, other income (loss), or income taxes.