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Short-Term and Long-Term Investments - Summary of Available-for-Sale Securities (Detail) - USD ($)
Sep. 30, 2015
Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]    
Cost $ 3,340,000 $ 3,700,000
Gross Unrealized Gains 1,000  
Gross unrealized losses 371,000 428,000
Estimated Fair Value 2,970,000 3,272,000
Failed Auction Security [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Cost 3,000,000 3,000,000
Gross unrealized losses 371,000 425,000
Estimated Fair Value 2,629,000 2,575,000
Brokered Certificates of Deposit [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Cost 340,000 700,000
Gross Unrealized Gains 1,000  
Gross unrealized losses   3,000
Estimated Fair Value $ 341,000 $ 697,000