Revenues -Narrative (Detail)	Sep. 30, 2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2019-10-01
Revenue From Contract With Customer [Line Items]
Remaining revenue performance obligation, percentage of revenue expected to be recognized	5.00%
Remaining performance obligations period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-01-01
Revenue From Contract With Customer [Line Items]
Remaining revenue performance obligation, percentage of revenue expected to be recognized	20.00%
Remaining performance obligations period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Revenue From Contract With Customer [Line Items]
Remaining revenue performance obligation, percentage of revenue expected to be recognized	20.00%
Remaining performance obligations period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01
Revenue From Contract With Customer [Line Items]
Remaining revenue performance obligation, percentage of revenue expected to be recognized	20.00%
Remaining performance obligations period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-01-01
Revenue From Contract With Customer [Line Items]
Remaining revenue performance obligation, percentage of revenue expected to be recognized	10.00%
Remaining performance obligations period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-01-01
Revenue From Contract With Customer [Line Items]
Remaining revenue performance obligation, percentage of revenue expected to be recognized	10.00%
Remaining performance obligations period	1 year