Revenue Recognition - Contract Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Customer receivables	$ 737	$ 712
Contract assets	31	19
Contract liabilities	412	393
Accounts receivable, gross	751	723
Allowance for doubtful accounts receivable	$ 14	$ 11

Amount, before allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business.

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Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business.

+ References

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Amount of allowance for credit loss on accounts receivable.

+ References

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Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

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Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

+ References

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