Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Federal corporate tax rate		35.00%	35.00%	35.00%
Net tax benefit recognized due to re-measurement of deferred tax liabilities		$ 102,800,000
Provisional income tax expense related to deemed repatriation of foreign earnings		300,000
Deferred tax liability related to foreign earnings		$ 0
Term of finalizing provision		1 year
Excess tax shortfall (benefit) from exercise of share-based awards		$ (900,000)	$ 1,100,000	$ 300,000
Likelihood percentage of being realized upon ultimate settlement with the relevant tax authority		50.00%
Unrecognized tax benefits		$ 0	0
Changes in unrecognized benefits		0	$ 0	$ 0
Foreign [Member]
Operating Loss Carryforwards [Line Items]
Net operating losses carryforwards		$ 400,000
Net operating losses carryforwards, expiration year		2023
Scenario Forecast [Member]
Operating Loss Carryforwards [Line Items]
Federal corporate tax rate	21.00%