Segment Information - Additional Information (Detail) - USD ($) $ in Billions	3 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Segment Reporting [Abstract]
Revenue in excess of billings	$ 0.2	$ 0.2
Total backlog	$ 2.9
Percentage of revenue expected to be recognized over next 12 months	49.00%
Billings and cash collections in excess of revenue	$ 1.0	$ 0.9

Amount of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

No definition available.

Name:	us-gaap_DeferredRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant