Amounts Currently Included in OCI in Consolidated Statement of Operations (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011
RIGP
Schedule of Pension and Other Postretirment Benefits Recgonized in Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of unrecognized losses	$ 1,389
Retiree Medical Plan
Schedule of Pension and Other Postretirment Benefits Recgonized in Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of unrecognized losses	1,036
Amortization of prior service cost benefit	$ (2,964)

The change in other comprehensive income due to the amortization of the net prior service costs (credit) into net periodic pension costs.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

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+ Details