XML 51 R40.htm IDEA: XBRL DOCUMENT v3.8.0.1
Long-Term Investments - Summary of Available-for-Sale Securities (Detail) - Failed Auction Security [Member] - USD ($)
Mar. 31, 2018
Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]    
Cost $ 3,000,000 $ 3,000,000
Gross Unrealized Gains 0 0
Gross Unrealized Losses 452,000 475,000
Estimated Fair Value $ 2,548,000 $ 2,525,000