Long-Term Cash Incentive Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2016	Dec. 31, 2017
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Performance condition period		3 years
Long Term Incentive Plan 2016
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Estimated payment of plan including employer cost	$ 4.4
Accrued compensation expense	$ 1.2	$ 1.9	$ 1.3