Oil and Gas Properties (Income (Loss) From Discontinued Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from discontinued operations, net of tax	$ (29)	$ 42,216		$ 1,029		$ 91,069
Helix [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from discontinued operations, net of tax	(29)			(14,753)
Energy Resource Technology GOM, Inc [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues		149,933		48,847	[1]	328,018
Production (lifting) costs		40,247		16,017	[1]	77,269
Exploration expense		1,092		3,514	[1]	1,846
Depreciation, depletion, amortization and accretion		39,730		1,226	[1]	87,572
Proved property impairment and abandonment		4,077		(152)	[1]	7,317
Loss on sale of oil and gas properties		236				1,714
Gain on commodity derivative contracts		(10,069)				(7,730)
Selling, general and administrative expense		3,002		1,229	[1]	6,283
Net interest expense and other		6,973	[2]	2,732	[1],[2]	14,250	[2]
Total costs		85,288		24,566	[1]	188,521
Pretax income from discontinued operations		64,645		24,281	[1]	139,497
Income tax provision		22,429		8,499	[1]	48,428
Income from operations of discontinued operations		42,216		15,782	[1]	91,069
Loss on sale of business, net of tax				(14,753)	[1]
Income from discontinued operations, net of tax		$ 42,216		$ 1,029	[1]	$ 91,069

[1] Results for 2013 primarily reflect the operating results from January 1, 2013 through February 6, 2013 when ERT was sold. There were no material results of operations for ERT during the three-month period ended June 30, 2013.

[2] Net interest expense of $2.7 million for the six-month period ended June 30, 2013, and $6.8 million and $14.0 million for the three- and six-month periods ended June 30, 2012, respectively, was allocated to ERT primarily based on interest associated with indebtedness directly attributed to the substantial oil and gas acquisition made in 2006. This includes interest related to debt required to be paid upon the disposition of ERT.