Consolidated Balance Sheets (Parenthetical) - $ / shares |
Dec. 31, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Statement Of Financial Position [Abstract] | ||
| Ordinary shares, par value (in dollars per share) | $ 0.001 | $ 0.001 |
| Ordinary shares, authorized | 490,000,000 | 490,000,000 |
| Ordinary shares, issued | 237,533,270 | 235,484,613 |
| Ordinary shares, outstanding | 213,082,411 | 217,650,644 |
| Ordinary shares, treasury stock | 24,450,859 | 17,833,969 |