Revenue - Unsatisfied Performance Obligation - Additional Information (Detail)	Sep. 30, 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2018-10-01
Revenue From Contract With Customer [Line Items]
Unsatisfied performance obligations, expected to recognize	19.00%
Unsatisfied performance obligations, expected to recognize, period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2019-01-01
Revenue From Contract With Customer [Line Items]
Unsatisfied performance obligations, expected to recognize	56.00%
Unsatisfied performance obligations, expected to recognize, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-01-01
Revenue From Contract With Customer [Line Items]
Unsatisfied performance obligations, expected to recognize	25.00%
Unsatisfied performance obligations, expected to recognize, period