Annual report pursuant to Section 13 and 15(d)

Income Taxes - Narrative (Details)

v3.8.0.1
Income Taxes - Narrative (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2017
USD ($)
Jurisdiction
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Income Tax Disclosure [Abstract]      
Estimated impact on net income (loss) $ 2,900    
Provisional income tax expense (benefit) 2,300    
Provisional investment valuation adjustment (946)    
Provisional income tax expense (benefit), investments (347)    
Estimated incremental income tax expense $ 1,900    
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Tax effect on common stock and additional paid in capital from employee stock purchase plan activity   $ (41) $ (44)
Expected U.S. federal income tax expense 35.00% 35.00% 35.00%
Unrecognized tax benefits that would impact effective rate $ 1,200 $ 600 $ 700
Number of jurisdictions for filing income tax returns (more than) | Jurisdiction 100    
Unrecognized tax benefits is reasonable possible, amount of unrecorded benefit $ 400    
Penalties and interest expense 1 56 (82)
Penalties and interest accrued 185 167  
Provisional undistributed accumulated earnings of foreign subsidiary 5,000    
Provisional unrecognized deferred tax liability 1,000    
Accumulated Other Comprehensive Income (Loss)      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Other comprehensive income (loss), tax $ 1,229 $ 498 $ (631)