Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Summary of Changes in Allowance for Credit Losses

The following table presents the changes in our allowance for credit losses for the periods presented:

	December 31,
	2020			2019			2018
	(in millions)
Allowance for doubtful accounts:
Balance, beginning of period	$	25		$	21		$	16
Provision charged to expense		17			11			11
Write-offs, net of recoveries and other    adjustments		(9	)		(7	)		(6	)
Balance, end of period	$	33		$	25		$	21