Income Taxes - Summary of Changes in Deferred Tax Asset Valuation Allowance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 68,661	$ 88,453	$ 70,629
Balance at End of Year	88,596	68,661	88,453
Valuation Allowance of Deferred Tax Assets
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Charged to Costs and Expenses	19,935	17,898	17,824
Write-offs	$ 0	$ (37,690)	$ 0