v3.19.3.a.u2
Income Taxes - Additional Information (Detail) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Mar. 31, 2019
Sep. 30, 2018
Mar. 31, 2018
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Income Taxes Disclosure [Line Items]            
Federal statutory tax rate       21.00% 21.00% 35.00%
Deferred tax asset       $ 796 $ 643  
Deferred income tax liabilities       3,734 3,571  
Discrete income tax benefit for vested stock awards $ 22   $ 56 28 64  
Discrete income tax benefit related to changes in organizational structure   $ 90     81  
Deferred tax assets, valuation allowance       51 68  
Income taxes receivable       282 282  
Income taxes payable       293 341  
Unrecognized tax benefits that would affect effective tax rate if recognized       513 462 $ 316
Interest and penalties accrued during period       27 30 17
Liability for interest and penalties       133 106 $ 76
Minimum [Member]            
Income Taxes Disclosure [Line Items]            
Liability for uncertain tax positions       5    
Maximum [Member]            
Income Taxes Disclosure [Line Items]            
Liability for uncertain tax positions       20    
Related to the Same Tax Jurisdiction [Member]            
Income Taxes Disclosure [Line Items]            
Deferred tax asset       175 163  
Deferred income tax liabilities       3,734 3,571  
State and Local Jurisdiction [Member]            
Income Taxes Disclosure [Line Items]            
Net operating loss carryforwards       $ 1,900 2,900  
Net operating loss carryforwards, maturity year       2020    
Foreign [Member]            
Income Taxes Disclosure [Line Items]            
Net operating loss carryforwards       $ 110 $ 76  
Net operating loss carryforwards, maturity year       2021    
Foreign net loss carry forwards, subject to expiration       $ 3