Income Taxes - Narrative (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Provisional income tax benefit related to the Tax Act	$ (45,800)
Provisional income tax expense related to repatriation of foreign earnings	2,100
Expected repatriation of foreign earnings related to the Tax Act	10,000
State and foreign net operating loss carry forwards	38,023	$ 34,478
State tax credits	9,965	8,890
Valuation allowance	21,755	12,048
Increase in valuation allowance	9,700
Unrecognized tax benefits that would impact effective tax rate	5,100
Unrecognized tax benefit that would be offset by tax benefits associated with transfer pricing adjustment	2,900
Unrecognized tax benefit with uncertainty about timing of deductibility	7,000
Accrued interest	2,000	$ 2,700
Decrease in deferred tax asset related to the Tax Act	$ 3,900
Minimum
Income Taxes [Line Items]
Period of income tax returns examination after filing	3 years
Maximum
Income Taxes [Line Items]
Period of income tax returns examination after filing	5 years
Resolution of uncertain tax positions | Minimum
Income Taxes [Line Items]
Decrease in gross liability for uncertain tax positions	$ 5,000
Resolution of uncertain tax positions | Maximum
Income Taxes [Line Items]
Decrease in gross liability for uncertain tax positions	$ 6,000