| Investments in an Unrealized Loss Position, Determined to be Temporarily Impaired (Detail) (USD $) In Thousands | Jun. 30, 2011 | 
|---|---|
| Fair Value | |
| Less than one year | $ 3,561 | 
| Greater than one year | 0 | 
| Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total | 3,561 | 
| Unrealized Losses | |
| Less than one year | 58 | 
| Greater than one year | 0 | 
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses, Total | $ 58 | 
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- Definition This item represents the excess of amortized cost basis over fair value of securities that have been in a loss position for twelve months or longer for those securities which are categorized neither as held-to-maturity nor trading securities. 
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- Definition This item represents the excess of amortized cost basis over fair value of securities in a loss position and which are categorized neither as held-to-maturity nor trading securities. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Details 
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- Definition This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Details 
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- Definition This item represents the excess of amortized cost basis over fair value of securities that have been in a loss position for less than twelve months for those securities which are categorized neither as held-to-maturity nor trading securities. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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| X | ||||||||||
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- Definition This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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| X | ||||||||||
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- Definition This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for twelve months or longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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