Income Taxes - Summary of Changes in Deferred Tax Assets Valuation Allowance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Beginning Balance	$ 61,456	$ 69,593	$ 89,251
Charged (credited) to provision for income taxes	14,156	(23,670)	(15,981)
Charged (credited) to other comprehensive income and other	(2,498)	15,533	(3,677)
Ending Balance	$ 73,114	$ 61,456	$ 69,593