Fair Value Measurements and Auction Rate Securities (Details) (USD $)	6 Months Ended	12 Months Ended
Jun. 30, 2012	Dec. 31, 2011
Auction Rate Securities [Line Items]
Auction rate securities par value	$ 1,975,000	$ 2,425,000
Maximum contract period, investments	35 years
Other than temporary impairment losses, investments	$ 469,000	$ 469,000
Minimum [Member]
Auction Rate Securities [Line Items]
Auction rate securities rate setting interval	7 days
Maximum [Member]
Auction Rate Securities [Line Items]
Auction rate securities rate setting interval	63 days

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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+ Details