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Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Fair Value of Financial Instruments [Line Items]
Investments not required to be disclosed	$ 338	$ 322
NUG contracts
Fair Value of Financial Instruments [Line Items]
Period of future observable data to determine contract price	2 years

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- Definition

Fair Value of Financial Instruments.

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- Definition

Investments not required to be disclosed.

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