Items to be Recognized in 2012 as a Component of Net Periodic Cost (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011
Pension Benefits
Items to be recognized in 2012 as a component of net periodic cost
Net actuarial loss	$ 12,351
Prior service cost (credit)	1,906
Net periodic cost (credit) to be recorded in 2012	14,257
Other Postretirement Benefits
Items to be recognized in 2012 as a component of net periodic cost
Net actuarial loss	278
Prior service cost (credit)	(2,616)
Net periodic cost (credit) to be recorded in 2012	$ (2,338)

The amounts in accumulated other comprehensive income related to gains and losses that are not recognized immediately and are expected to be recognized as components of net periodic benefit cost over the next fiscal year that follows the most recent annual statement of financial position presented.

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The amounts in accumulated other comprehensive income related to prior service cost or credit expected to be recognized as components of net periodic benefit cost over the next fiscal year that follows the most recent annual statement of financial position presented.

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- Definition

The aggregate amount in accumulated other comprehensive income expected to be recognized as a component of net periodic benefit cost over the fiscal year that follows the most recent annual statement of financial position presented, including the net gain (loss), net prior service cost or credit, and net transition asset or obligation.

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