Commitments and Contingencies (Details) - USD ($) $ in Millions	Apr. 20, 2021	Oct. 27, 2020	Jun. 30, 2021	Dec. 31, 2020	Mar. 31, 2019
Other Commitments [Line Items]
Accrued Liabilities and Other Liabilities			$ 2,234	$ 2,519
Insurance receivable for malpractice			$ 10	$ 7
Syntel Sterling Best Shores Mauritius Ltd. [Member]
Other Commitments [Line Items]
Litigation settlement, amount awarded from other party	$ 570	$ 855
Litigation Settlement Amount Awarded From Other Party, Punitive Damages	285	$ 570
Litigation Settlement Amount Awarded From Other Party, Actual Damages	$ 285
India Defined Contribution Obligation [Member]
Other Commitments [Line Items]
Accrued Liabilities and Other Liabilities					$ 117