Income Taxes (Narrative) (One-time Transaction) (Details) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2014 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 INR (₨)	Dec. 31, 2019 USD ($)	Apr. 30, 2018 INR (₨)
One-time Transaction [Table] [Line Items]
Income tax expense	$ 134	$ 167			$ 276	$ 309
Restricted investments								$ 414
Short-term Investments [Member]
One-time Transaction [Table] [Line Items]
Restricted investments								414
Long-term investments [Member]
One-time Transaction [Table] [Line Items]
Restricted investments	391				391
Indian Income Tax Department (ITD) [Member] | Foreign tax authority [Member]
One-time Transaction [Table] [Line Items]
Deposits assets	$ 66				$ 66		₨ 5,000,000,000	70
Desposits assets, percent disputed tax amount	15.00%				15.00%		15.00%
Restricted investments initially deposited	$ 371				$ 371			393	₨ 28,000,000,000
Indian Income Tax Department (ITD) [Member] | Foreign tax authority [Member] | Other Current Assets [Member]
One-time Transaction [Table] [Line Items]
Deposits assets								$ 70
Indian Income Tax Department (ITD) [Member] | Foreign tax authority [Member] | Other Noncurrent Assets [Member]
One-time Transaction [Table] [Line Items]
Deposits assets	66				66
Indian Income Tax Department (ITD) [Member] | Foreign tax authority [Member] | 2016 India Cash Remittance [Member]
One-time Transaction [Table] [Line Items]
Foreign earnings repatriated			$ 2,800
Income tax expense			$ 135
Income tax, disputed amount	$ 437				$ 437		₨ 33,000,000,000
Indian Income Tax Department (ITD) [Member] | Foreign tax authority [Member] | 2013 India Share Repurchase [Member]
One-time Transaction [Table] [Line Items]
Foreign earnings repatriated				$ 523