Income Taxes (Details) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2016 |
Mar. 31, 2015 |
|
| Income Tax Disclosure [Abstract] | ||
| Income tax expense | $ 559 | $ 529 |
| Tax expense, entities included in effective tax rate calculation | 775 | |
| Net deferred tax assets | $ 35,800 | |