Income Taxes - Narrative (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Operating loss carryforward	$ 2,400,000
Tax credit carryforwards	120,594	$ 75,879
Tax credit carryforwards	1,300,000
Deferred tax assets, gross	1,428,173	690,846
Valuation allowance comparison	754,100
Total unrecognized tax benefit	27,591	27,648	$ 18,440	$ 11,737
Unrecognized tax benefits that would impact effective tax rate	4,700
Unrecognized tax benefits, income tax interest and penalties accrued	300	500
Federal
Income Taxes [Line Items]
Tax credit carryforwards	89,700
State
Income Taxes [Line Items]
Tax credit carryforwards	65,200
Foreign Tax Authority
Income Taxes [Line Items]
Deferred tax assets, gross	18,700
Valuation allowance comparison		$ (106,900)	$ 607,000
Increase in deferred tax assets related to foreign restructuring	$ 590,000