Employee Benefit Plans - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Provision for contributions to the Supplemental Plan	$ 256,000	$ 245,000	$ 238,000
US Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, employer profit sharing contribution percent	4.00%	4.00%	4.00%
Vesting period for the profit sharing contribution	3 years
Defined contribution plan, cost recognized	25,900,000	21,500,000	23,800,000
Defined Contribution Plan, Matching Contribution per employee by the company	6.00%	6.00%	6.00%
UK Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	2,700,000	1,200,000	1,200,000
UK Plan [Member] | U. K. Sector of North Sea [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Matching Contribution by the company	10.00%	5.25%	5.25%
UK Plan [Member] | U.K. Norwegian Sector of North Sea [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Matching Contribution by the company	15.00%	9.00%	9.00%
International Savings Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, employer profit sharing contribution percent	4.00%	4.00%	4.00%
Defined contribution plan, cost recognized	$ 2,800,000	$ 2,900,000	$ 2,800,000
Defined Contribution Plan, Matching Contribution per employee by the company	6.00%	6.00%	6.00%