Financial Instruments And Fair Value Disclosures (Narrative) (Detail) (USD $)	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts receivable expected to be collected within one year	$ 42,200,000	$ 95,800,000
Net profits interest percent	27.00%
Allowance for bad debts	(5,470,000)	(6,867,000)
Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments	292,800,000	303,900,000
Level 1 [Member] | US Treasury Bill Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments	1,175,300,000	902,000,000
5.70% Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate of senior notes	5.70%	5.70%
5.875% Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate of senior notes	5.875%	5.875%
4.875% Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate of senior notes	4.875%	4.875%
5.15% Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate of senior notes	5.15%	5.15%
Petrobras [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts receivable due from major customer	107,800,000	110,400,000
Percentage of accounts receivable due from major customer	24.00%	20.00%
OGX [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts receivable due from major customer	$ 50,200,000	$ 69,400,000
Percentage of accounts receivable due from major customer	11.00%	12.00%