Reconciliation of Plans' Benefit Obligations and Fair Value of Assets and Statement of Funded Status (Detail) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Change in plan assets
Fair value of plan assets, Ending Balance	$ 404,350,000	$ 416,272,000
Pension Benefits
Change in benefit obligation
Obligations, Beginning Balance	575,300,000	521,471,000
Service cost	22,406,000	20,706,000	17,052,000
Interest cost	30,785,000	30,144,000	28,767,000
Plan amendments	483,000	0
Participant contributions	35,000	33,000
Actuarial loss	66,010,000	30,544,000
Medicare Part D subsidy	0	0
Exchange rate changes	(2,109,000)	(1,357,000)
Benefits paid	(27,745,000)	(26,241,000)
Reduction due to sale of the Superior refinery	(23,021,000)	0
Special termination benefits	695,000	0	1,867,000
Curtailments	(13,271,000)	0
Obligations, Ending Balance	629,568,000	575,300,000	521,471,000
Change in plan assets
Fair value of plan assets, Beginning Balance	416,272,000	375,947,000
Actual return on plan assets	(1,415,000)	46,792,000
Employer contributions	38,357,000	20,651,000
Participant contributions	35,000	33,000
Medicare Part D subsidy	0	0
Exchange rate changes	(1,786,000)	(422,000)
Benefits paid	(27,745,000)	(26,241,000)
Distribution to acquirer of the Superior refinery	(18,720,000)	0
Other	(648,000)	(488,000)
Fair value of plan assets, Ending Balance	404,350,000	416,272,000	375,947,000
Funded status and amounts recognized in the Consolidated Balance Sheets at end of the period
Deferred charges and other assets	10,621,000	14,191,000
Other accrued liabilities	(3,488,000)	(3,378,000)
Deferred credits and other liabilities	(232,351,000)	(169,841,000)
Funded status and net plan liability recognized at the end of the period	(225,218,000)	(159,028,000)
Other Postretirement Benefits
Change in benefit obligation
Obligations, Beginning Balance	122,879,000	101,750,000
Service cost	4,547,000	4,133,000	3,121,000
Interest cost	6,141,000	6,211,000	5,688,000
Plan amendments	0	0
Participant contributions	1,049,000	956,000
Actuarial loss	4,791,000	14,646,000
Medicare Part D subsidy	555,000	528,000
Exchange rate changes	(11,000)	22,000
Benefits paid	(5,667,000)	(5,367,000)
Reduction due to sale of the Superior refinery	0	0
Special termination benefits	0	0	0
Curtailments	(19,322,000)	0
Obligations, Ending Balance	114,962,000	122,879,000	101,750,000
Change in plan assets
Fair value of plan assets, Beginning Balance	0	0
Actual return on plan assets	0	0
Employer contributions	4,063,000	3,883,000
Participant contributions	1,049,000	956,000
Medicare Part D subsidy	555,000	528,000
Exchange rate changes	0	0
Benefits paid	(5,667,000)	(5,367,000)
Distribution to acquirer of the Superior refinery	0	0
Other	0	0
Fair value of plan assets, Ending Balance	0	0	0
Funded status and amounts recognized in the Consolidated Balance Sheets at end of the period
Deferred charges and other assets	0	0
Other accrued liabilities	(5,022,000)	(5,223,000)
Deferred credits and other liabilities	(109,940,000)	(117,656,000)
Funded status and net plan liability recognized at the end of the period	$ (114,962,000)	$ (122,879,000)