Income Taxes - Additional Information (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | 12 Months Ended | |||
|---|---|---|---|---|---|---|
Jun. 30, 2018 |
Mar. 31, 2018 |
Jun. 30, 2017 |
Jun. 30, 2018 |
Jun. 30, 2017 |
Dec. 31, 2017 |
|
| Income Tax Disclosure [Abstract] | ||||||
| Provision for income taxes | $ 301 | $ 430 | $ 488 | $ 688 | ||
| Estimated annual effective tax rate | 20.00% | 31.00% | 20.00% | 31.00% | ||
| Statutory corporate tax rate | 21.00% | |||||
| Additional tax expense | $ 773 | |||||
| Non-U.S. earnings, Increase (decrease) in income tax expense | $ 669 | 714 | ||||
| Remeasurement of deferred tax balance | $ 50 | $ 59 | ||||