Segment Information - Geographical Segment Revenue (Detail) - USD ($) $ in Thousands |
3 Months Ended | 12 Months Ended | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2017 |
Sep. 30, 2017 |
Jun. 30, 2017 |
Mar. 31, 2017 |
Dec. 31, 2016 |
Sep. 30, 2016 |
Jun. 30, 2016 |
Mar. 31, 2016 |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
Revenues from External Customers and Long-Lived Assets [Line Items] | |||||||||||
Total | $ 4,858 | $ 8,677 | $ 5,587 | $ 6,091 | $ 5,180 | $ 5,576 | $ 5,457 | $ 5,580 | $ 25,213 | $ 21,793 | $ 22,189 |
Domestic [Member] | |||||||||||
Revenues from External Customers and Long-Lived Assets [Line Items] | |||||||||||
Total | 5,116 | 4,776 | 6,304 | ||||||||
International [Member] | |||||||||||
Revenues from External Customers and Long-Lived Assets [Line Items] | |||||||||||
Total | $ 20,097 | $ 17,017 | $ 15,885 |