Quantitative Information about Level 3 Fair Value Measurements (Detail) (USD $) In Thousands, unless otherwise specified			12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Discounted Cash Flow [Member] Unobservable Inputs (Level 3) [Member] Derivative Financial Instruments, Liabilities [Member] Minimum [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] Unobservable Inputs (Level 3) [Member] Derivative Financial Instruments, Liabilities [Member] Maximum [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair value inputs, long dated treasuries			2.82%	2.91%
Fair value inputs, own credit risk			0.98%	1.59%
Quantitative Fair Value at December 31, 2012	$ (826)	$ (1,667)

This element represents the aggregate of the liabilities reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

Name:	us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant