Current Prepaid Expenses - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2018
Short Term [Member] | Minimum [Member]
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Line Items]
Current prepaid expense recognition period - subscription projects	3 months
Short Term [Member] | Maximum [Member]
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Line Items]
Current prepaid expense recognition period - subscription projects	12 months
Long Term [Member] | Minimum [Member]
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Line Items]
Current prepaid expense recognition period - subscription projects	1 year
Long Term [Member] | Maximum [Member]
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Line Items]
Current prepaid expense recognition period - subscription projects	3 years