Retirement Agreement - Additional Information (Detail) - Chief Executive Officer [Member] - USD ($) $ in Millions	Jan. 15, 2018	Jan. 02, 2018	Sep. 05, 2017
Defined Benefit Plan Disclosure [Line Items]
Payment for retirement benefit			$ 0.8
Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Payment for retirement benefit	$ 0.8	$ 0.2
Vested shares		250,000
Vesting rights, percentage		100.00%
Scenario, Forecast [Member] | CIC Retirement Payment [Member]
Defined Benefit Plan Disclosure [Line Items]
Payment for retirement benefit		$ 0.2
Payment period after retirement date		10 days
Scenario, Forecast [Member] | Additional Retirement Payment [Member]
Defined Benefit Plan Disclosure [Line Items]
Payment for retirement benefit		$ 0.2
Change in control period considered after retirement date		12 months