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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Derivatives (Details) - USD ($) $ in Millions	6 Months Ended
Derivatives (Details) - USD ($) $ in Millions	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Derivative [Line Items]
Cash received for partial termination of 1.125% Call Option	$ 134	$ 0
Cash paid for partial termination of 1.125% Warrants	113	$ 0
Debt conversion, net cash receipts	$ 21
1.125% Convertible Notes
Derivative [Line Items]
Percentage of contractual interest rate on Notes	1.125%
1.125% Call Option
Derivative [Line Items]
Percentage of contractual interest rate on Call Option	1.125%
1.125% Conversion Option derivative liability
Derivative [Line Items]
Percentage of contractual interest rate on Call Option	1.125%
Cash received for partial termination of 1.125% Call Option	$ 134
Current assets: Derivative asset \| 1.125% Call Option
Derivative [Line Items]
Derivative assets	657		$ 522
Current liabilities: Derivative liability \| 1.125% Conversion Option derivative liability
Derivative [Line Items]
Derivative liabilities	657		$ 522
Cash Convertible Senior Notes Due 2020, Warrants
Derivative [Line Items]
Cash paid for partial termination of 1.125% Warrants	$ 113