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Short-Term and Long-Term Investments - Rollforward of Credit (Gain) Loss Recognized in Earnings on Available-for-Sale Auction Rate Securities (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Available-for-sale Securities, Debt Maturities [Abstract]      
Balance at the beginning of the period $ 84 $ 395 $ 317
Reductions for securities sold during the period   (272) (7)
Additions (reductions) for the amount related to credit loss for which other-than-temporary impairment was not previously recognized (12) (39) 85
Balance at the end of the period $ 72 $ 84 $ 395