Deferred Revenue (Tables)

6 Months Ended

Jun. 30, 2020

Revenue Recognition And Deferred Revenue [Abstract]

Summary of Deferred Revenue Activity

Deferred revenue activity consists of the following (dollars in millions):

	Three Months Ended June 30,						Six Months Ended June 30,
	2020			2019			2020			2019
Beginning balance	$	140		$	131		$	139		$	122
Increases		13			11			24			29
Revenue earned		(8	)		(9	)		(18	)		(18	)
Ending balance	$	145		$	133		$	145		$	133