Revenue Recognition - Estimated Revenue Expected to be Recognized in Future Related to Performance Obligations (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
2018
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Estimated revenue, expected recognition period	1 year
2019
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Estimated revenue, expected recognition period	1 year
2020
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Estimated revenue, expected recognition period	1 year
2021
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Estimated revenue, expected recognition period	1 year
Software [Member] | 2018 | Third-Party Software [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Estimated revenue expected to be recognized in future	$ 110
Software [Member] | 2018 | Proprietary Software [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Estimated revenue expected to be recognized in future	2,655
Software [Member] | 2019 | Third-Party Software [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Estimated revenue expected to be recognized in future	36
Software [Member] | 2019 | Proprietary Software [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Estimated revenue expected to be recognized in future	1,133
Software [Member] | 2020 | Proprietary Software [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Estimated revenue expected to be recognized in future	820
Software [Member] | 2021 | Proprietary Software [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Estimated revenue expected to be recognized in future	114
Professional Engineering Services [Member] | 2018
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Estimated revenue expected to be recognized in future	$ 760