Income Taxes - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018 USD ($) Tax_Positions	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Income Tax Contingency [Line Items]
Statutory tax rate, percentage	21.00%
Deferred tax assets, liability		$ 1,900,000
Valuation allowance	$ 3,015,000	3,096,000
Income tax expense (benefit)	$ 42,289,000	46,791,000	$ 34,983,000
Unrecognized tax benefits number of tax matters | Tax_Positions	0
Unrecognized tax benefits related to identified uncertain tax positions	$ 0
Tax years subject to examination	2015 2016 2017 2018
Accounting Standards Update 2016-09 [Member]
Income Tax Contingency [Line Items]
Income tax expense (benefit)	$ 2,400,000	$ 1,500,000