Capital Stock - Common and Preferred Stock Authorized (Detail) - shares |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Class of Stock [Line Items] | ||
| Common stock, shares authorized | 500,000,000 | 500,000,000 |
| Series A Nonvoting Participating Preferred Stock [Member] | ||
| Class of Stock [Line Items] | ||
| Preferred stock, shares authorized | 20,000,000 | |
| Series B Nonvoting Participating Preferred Stock [Member] | ||
| Class of Stock [Line Items] | ||
| Preferred stock, shares authorized | 0 | 150,000,000 |
| Series C Nonvoting Participating Preferred Stock [Member] | ||
| Class of Stock [Line Items] | ||
| Preferred stock, shares authorized | 6,000,000 | |
| Series D Nonvoting Participating Preferred Stock [Member] | ||
| Class of Stock [Line Items] | ||
| Preferred stock, shares authorized | 20,000,000 |