XML 56 R41.htm IDEA: XBRL DOCUMENT v3.10.0.1
Fair Value Measurements - Carrying Value and Fair Value of Certain Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)
Dec. 31, 2018
Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Long-term restricted cash equivalents $ 0 $ 6,336,000
Trading securities 0 3,761,000
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash and cash equivalents 7,703,000 20,751,000
Long-term restricted cash equivalents 500,000 6,336,000
Trading securities   3,761,000
Marketable securities - held-to-maturity 37,955,000  
Debt Instrument, Fair Value Disclosure 5,060,000  
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | US Government Agencies Debt Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Marketable securities - held-to-maturity 21,473,000  
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | US Treasury Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Marketable securities - held-to-maturity 16,482,000  
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | Certificates of deposit [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Marketable securities - held-to-maturity   4,452,000
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash and cash equivalents 7,703,000 20,751,000
Long-term restricted cash equivalents 500,000 6,336,000
Trading securities   3,761,000
Marketable securities - held-to-maturity 37,955,000  
Debt Instrument, Fair Value Disclosure 0  
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash and cash equivalents 0 0
Long-term restricted cash equivalents 0 0
Trading securities   0
Marketable securities - held-to-maturity 0  
Debt Instrument, Fair Value Disclosure 0  
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash and cash equivalents 0 0
Long-term restricted cash equivalents 0 0
Trading securities   0
Marketable securities - held-to-maturity 0  
Debt Instrument, Fair Value Disclosure 5,060,000  
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | US Government Agencies Debt Securities [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Marketable securities - held-to-maturity 21,473,000  
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | US Government Agencies Debt Securities [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Marketable securities - held-to-maturity 0  
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | US Government Agencies Debt Securities [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Marketable securities - held-to-maturity 0  
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | US Treasury Securities [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Marketable securities - held-to-maturity 16,482,000  
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | US Treasury Securities [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Marketable securities - held-to-maturity 0  
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | US Treasury Securities [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Marketable securities - held-to-maturity $ 0  
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Certificates of deposit [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Marketable securities - held-to-maturity   4,452,000
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Certificates of deposit [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Marketable securities - held-to-maturity   0
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Certificates of deposit [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Marketable securities - held-to-maturity   $ 0