Share-based Payments - Summary of Black-Scholes Option-Pricing Models (Details) - $ / shares |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Disclosure Of Share Based Payments [Line Items] | |||
| Weighted-average share price (US$) | $ 136.09 | $ 142.20 | $ 64.11 |
| Bottom of Range | |||
| Disclosure Of Share Based Payments [Line Items] | |||
| Expected volatility (%) | 30.10% | 32.00% | 32.00% |
| Risk-free interest rate (%) | 1.40% | 2.40% | 1.40% |
| Expected life of stock options (years) | 2 years 6 months | 2 years 4 months 24 days | 2 years 4 months 24 days |
| Top of Range | |||
| Disclosure Of Share Based Payments [Line Items] | |||
| Expected volatility (%) | 35.20% | 34.70% | 43.50% |
| Risk-free interest rate (%) | 2.60% | 2.90% | 2.00% |
| Expected life of stock options (years) | 4 years 8 months 12 days | 4 years 4 months 24 days | 4 years 4 months 24 days |