Income Taxes - Additional Information (Detail) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Income Tax Disclosure [Abstract] | ||
| Combined federal, state and foreign income tax rate | 9.00% | 29.00% |
| Statutory rate applied to income before income taxes | 21.00% | 35.00% |
| Unrecognized benefits | $ 19 | |