Revenue from Contracts with Customers - Estimate at Completion Adjustments (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Change in Accounting Estimate [Line Items]
Total revenues	$ 681	$ 583
Contracts Accounted for under Percentage of Completion
Change in Accounting Estimate [Line Items]
Total revenues	$ (1)	$ (3)
Total % of Revenue	0.00%	1.00%

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details