Stockholders' Equity - Additional Information (Detail) - USD ($) |
Mar. 31, 2018 |
Sep. 20, 2016 |
Sep. 16, 2013 |
|---|---|---|---|
| Share Repurchase Program 2013 | |||
| Share Repurchases [Line Items] | |||
| Amount available for repurchase under the share repurchase program approved by the company's Board of Directors | $ 40,000,000,000 | ||
| Share Repurchase Program 2016 | |||
| Share Repurchases [Line Items] | |||
| Amount available for repurchase under the share repurchase program approved by the company's Board of Directors | $ 40,000,000,000 | ||
| Unused amount of share repurchase program | $ 30,300,000,000 |