Components of Net Periodic Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Accumulated Other Comprehensive Income Loss After Tax [Line Items]
Unamortized net loss	$ 2,154	$ 2,107
Unamortized prior service cost	15	30
Defined benefit plan, accumulated other comprehensive income (Loss), after tax	$ 2,169	$ 2,137

After tax total of net gain (loss), prior service cost (credit), and transition assets (obligations), as well as minimum pension liability if still remaining, included in accumulated other comprehensive income associated with a defined benefit pension or other postretirement plan(s).

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant