Long-Term Debt (Narrative) (Details) (USD $)	3 Months Ended	9 Months Ended								9 Months Ended										1 Months Ended	3 Months Ended	1 Months Ended	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2011	Sep. 30, 2010	Aug. 31, 2011	Jun. 30, 2011	May 31, 2011	Mar. 31, 2011	Dec. 31, 2010	Mar. 31, 2010	Sep. 30, 2011 Maximum [Member] Helix Term Loan [Member]	Sep. 30, 2011 Maximum [Member] Helix Revolving Loans [Member]	Sep. 30, 2011 Minimum [Member] Helix Term Loan [Member]	Sep. 30, 2011 Minimum [Member] Helix Revolving Loans [Member]	Sep. 30, 2011 Helix Term Loan [Member]	Sep. 30, 2010 Helix Term Loan [Member]	Jul. 31, 2006 Helix Term Loan [Member]	Sep. 30, 2011 Revolving Credit Facility [Member]	Sep. 30, 2011 Helix Revolving Loans [Member]	Jul. 31, 2006 Helix Revolving Loans [Member]	Dec. 31, 2007 Senior Unsecured Notes [Member]	Sep. 30, 2011 Senior Unsecured Notes [Member]	Mar. 31, 2005 Convertible Senior Notes [Member]	Sep. 30, 2011 Convertible Senior Notes [Member]		Sep. 30, 2011 MARAD Debt [Member]		Sep. 30, 2011 Credit Agreement [Member]	Sep. 30, 2011 Letters Of Credit [Member]
Unsecured letters of credit	$ 42,600,000	$ 42,600,000																										$ 42,600,000
Long-term debt, noncurrent	1,163,914,000	1,163,914,000						1,347,753,000						295,500,000						550,000,000	474,960,000		288,165,000	[1]	105,289,000
Long-term debt, Carrying Value	1,183,626,000	1,183,626,000																			474,960,000	300,000,000	300,000,000	[2]	110,166,000	[3]
Long Term Debt																835,000,000
Debt instrument interest rate																				9.50%					4.93%
Stated maturity Year																				2016			March 2025		February 2027
Aggregate amount of debt payment	77,400,000	77,394,000
Payment on senior unsecured notes																					75,000,000
Accrued interest on notes	800,000	73,096,000	60,137,000
Loss on early extinguishment of Senior Unsecured Notes	2,400,000	2,354,000
Original borrowing capacity					600,000,000	435,000,000													300,000,000
Cash and cash equivalents plus available capacity under revolving credit facility																					500,000,000		400,000,000
Margin range										3.50%	3.50%	3.25%	2.50%
Revolving credit facility, outstanding																	0
Base rate range										2.50%	2.50%	2.25%	1.50%
Average interest rate														3.60%	2.90%
Revolving credit facility available	557,400,000	557,400,000
Investments in Subsidiaries Permitted by Credit Agreement, Excluding Loan Party Subsidiaries and Subsidiaries With Pledged Equity Interests					200,000,000	150,000,000
Repurchases and Redemptions Permitted Under Credit Agreement, Common Stock, Value																		50,000,000
Interest rate swap	200,000,000	200,000,000		200,000,000
Debt instrument issued percentage																						100.00%
Effective interest rate																							6.60%
Per share conversion price							$ 32.14		$ 32.14
Convertible senior notes are convertible into shares																							13,303,770
Debt instrument, frequency of periodic payment																									semi-annual
Debt collateral percentage		50.00%
Deferred financing costs, net	28,013,000	28,013,000						25,697,000																			9,200,000
Amortization of deferred financing costs	900,000	7,197,000	5,731,000																		900,000						800,000
Repayment of revolving credit facility		$ 109,400,000												$ 109,400,000

[1] Beginning in December 2012, the holders may require us to repurchase the notes or we may at our own option elect to repurchase the notes. The notes will mature in March 2025.

[2] Amount excludes the $11.8 million of unamortized discount remaining on the Convertible Senior Notes at September 30, 2011.

[3] The estimated fair value of all debt, other than MARAD Debt, was determined using Level 1 inputs using the market approach. The fair value of the MARAD debt was determined using a third party evaluation of the remaining average life and outstanding principal balance of the MARAD indebtedness as compared to other governmental obligations in the market place with similar terms. The fair value of the MARAD debt was estimated using Level 2 fair value inputs using the cost approach.