Income Taxes - Summary of Activity Related to Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands |
12 Months Ended | |
|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Income Tax Uncertainties [Abstract] | ||
| Beginning balance of unrecognized tax benefits | $ 203,177 | $ 243,862 |
| Additions for current year tax positions | 43,197 | 42,209 |
| Additions for prior year tax positions | 7,615 | 2,158 |
| Reductions for prior year tax positions | (1,965) | (568) |
| Changes due to foreign currency translation adjustments | (216) | 163 |
| Remeasurement of uncertain tax positions due to the Tax Act | (84,647) | |
| Ending balance of unrecognized tax benefits (excluding interest and penalties) | 251,808 | 203,177 |
| Interest and penalties associated with unrecognized tax benefits | 260 | 80 |
| Ending balance of unrecognized tax benefits (including interest and penalties) | $ 252,068 | $ 203,257 |