The value of the financial instrument(s) that the original debt is being converted into in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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The cash inflow from the issuance of a long-term debt instrument which can be exchanged for a specified amount of another security, typically the entity's common stock, at the option of the issuer or the holder.

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Derivatives (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Derivatives (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Cash received for partial termination of 1.125% Call Option		$ 578	$ 477
Cash paid for partial termination of 1.125% Warrants		514	$ 419
Debt conversion, net cash receipts	$ 15	$ 64
1.125% Convertible Notes
Derivative [Line Items]
Percentage of contractual interest rate on notes	1.125%	1.125%
Percentage of contractual interest rate on Call Option	1.125%	1.125%
1.125% Call Option
Derivative [Line Items]
Percentage of contractual interest rate on Call Option	1.125%	1.125%		1.125%	1.125%
Cash received for partial termination of 1.125% Call Option	$ 105
1.125% Conversion Option
Derivative [Line Items]
Percentage of contractual interest rate on Call Option	1.125%	1.125%			1.125%
Current assets: Derivative asset \| 1.125% Call Option
Derivative [Line Items]
Derivative assets	$ 21	$ 21			$ 476
Current liabilities: Derivative liability \| 1.125% Conversion Option
Derivative [Line Items]
Derivative liabilities	$ 21	$ 21			$ 476
1.125% Warrants
Derivative [Line Items]
Percentage of contractual interest rate on Call Option	1.125%	1.125%		1.125%
Cash paid for partial termination of 1.125% Warrants	$ 90