Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Changes in Accumulated Other Comprehensive Income, Net of Income Taxes (Detail)

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Stockholders' Equity - Changes in Accumulated Other Comprehensive Income, Net of Income Taxes (Detail)
$ in Thousands
 6 Months Ended
Jun. 30, 2018
USD ($)
Accumulated Other Comprehensive Income (Loss) [Line Items]  
Beginning Balance $ 314,888
Balance as adjusted 314,888
Ending Balance 358,897
Unrealized gains and (losses) of available-for-sale securities [Member]  
Accumulated Other Comprehensive Income (Loss) [Line Items]  
Balance as adjusted (75)
Other comprehensive (loss) income before reclassifications (664)
Amounts reclassified from accumulated other comprehensive (loss) income 8
Net current-period other comprehensive (loss) income (656)
Ending Balance (731)
Unrealized gains and (losses) of available-for-sale securities [Member] | Previously Reported [Member]  
Accumulated Other Comprehensive Income (Loss) [Line Items]  
Beginning Balance (62)
Unrealized gains and (losses) of available-for-sale securities [Member] | Scenario, Adjustment [Member]  
Accumulated Other Comprehensive Income (Loss) [Line Items]  
Cumulative effect of change in accounting principle (13)
Foreign currency translation [Member]  
Accumulated Other Comprehensive Income (Loss) [Line Items]  
Balance as adjusted 1,002
Other comprehensive (loss) income before reclassifications 73
Amounts reclassified from accumulated other comprehensive (loss) income 0
Net current-period other comprehensive (loss) income 73
Ending Balance 1,075
Foreign currency translation [Member] | Previously Reported [Member]  
Accumulated Other Comprehensive Income (Loss) [Line Items]  
Beginning Balance 1,002
Foreign currency translation [Member] | Scenario, Adjustment [Member]  
Accumulated Other Comprehensive Income (Loss) [Line Items]  
Cumulative effect of change in accounting principle 0
Accumulated Other Comprehensive Income [Member]  
Accumulated Other Comprehensive Income (Loss) [Line Items]  
Beginning Balance 940
Balance as adjusted 927
Other comprehensive (loss) income before reclassifications (591)
Amounts reclassified from accumulated other comprehensive (loss) income 8
Net current-period other comprehensive (loss) income (583)
Ending Balance 344
Accumulated Other Comprehensive Income [Member] | Previously Reported [Member]  
Accumulated Other Comprehensive Income (Loss) [Line Items]  
Beginning Balance 940
Accumulated Other Comprehensive Income [Member] | Scenario, Adjustment [Member]  
Accumulated Other Comprehensive Income (Loss) [Line Items]  
Cumulative effect of change in accounting principle $ (13)