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Long-Term Investments - Summary of Available-for-Sale Securities (Detail) - USD ($)
Dec. 31, 2016
Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]    
Cost   $ 3,340,000
Gross Unrealized Gains   0
Gross unrealized losses   474,000
Estimated Fair Value   2,866,000
Failed Auction Security [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Cost $ 3,000,000 3,000,000
Gross Unrealized Gains 0 0
Gross unrealized losses 492,000 474,000
Estimated Fair Value $ 2,508,000 2,526,000
Brokered Certificates of Deposit [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Cost   340,000
Gross Unrealized Gains   0
Estimated Fair Value   $ 340,000